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# Copyright 2001-2013 Python Software Foundation; All Rights Reserved 

"""Function signature objects for callables 

 

Back port of Python 3.3's function signature tools from the inspect module, 

modified to be compatible with Python 2.6, 2.7 and 3.3+. 

""" 

from __future__ import absolute_import, division, print_function 

import itertools 

import functools 

import re 

import types 

 

try: 

from collections import OrderedDict 

except ImportError: 

from ordereddict import OrderedDict 

 

from funcsigs.version import __version__ 

 

__all__ = ['BoundArguments', 'Parameter', 'Signature', 'signature'] 

 

 

_WrapperDescriptor = type(type.__call__) 

_MethodWrapper = type(all.__call__) 

 

_NonUserDefinedCallables = (_WrapperDescriptor, 

_MethodWrapper, 

types.BuiltinFunctionType) 

 

 

def formatannotation(annotation, base_module=None): 

if isinstance(annotation, type): 

if annotation.__module__ in ('builtins', '__builtin__', base_module): 

return annotation.__name__ 

return annotation.__module__+'.'+annotation.__name__ 

return repr(annotation) 

 

 

def _get_user_defined_method(cls, method_name, *nested): 

try: 

if cls is type: 

return 

meth = getattr(cls, method_name) 

for name in nested: 

meth = getattr(meth, name, meth) 

except AttributeError: 

return 

else: 

if not isinstance(meth, _NonUserDefinedCallables): 

# Once '__signature__' will be added to 'C'-level 

# callables, this check won't be necessary 

return meth 

 

 

def signature(obj): 

'''Get a signature object for the passed callable.''' 

 

if not callable(obj): 

raise TypeError('{0!r} is not a callable object'.format(obj)) 

 

if isinstance(obj, types.MethodType): 

sig = signature(obj.__func__) 

if obj.__self__ is None: 

# Unbound method - preserve as-is. 

return sig 

else: 

# Bound method. Eat self - if we can. 

params = tuple(sig.parameters.values()) 

 

if not params or params[0].kind in (_VAR_KEYWORD, _KEYWORD_ONLY): 

raise ValueError('invalid method signature') 

 

kind = params[0].kind 

if kind in (_POSITIONAL_OR_KEYWORD, _POSITIONAL_ONLY): 

# Drop first parameter: 

# '(p1, p2[, ...])' -> '(p2[, ...])' 

params = params[1:] 

else: 

if kind is not _VAR_POSITIONAL: 

# Unless we add a new parameter type we never 

# get here 

raise ValueError('invalid argument type') 

# It's a var-positional parameter. 

# Do nothing. '(*args[, ...])' -> '(*args[, ...])' 

 

return sig.replace(parameters=params) 

 

try: 

sig = obj.__signature__ 

except AttributeError: 

pass 

else: 

if sig is not None: 

return sig 

 

try: 

# Was this function wrapped by a decorator? 

wrapped = obj.__wrapped__ 

except AttributeError: 

pass 

else: 

return signature(wrapped) 

 

if isinstance(obj, types.FunctionType): 

return Signature.from_function(obj) 

 

if isinstance(obj, functools.partial): 

sig = signature(obj.func) 

 

new_params = OrderedDict(sig.parameters.items()) 

 

partial_args = obj.args or () 

partial_keywords = obj.keywords or {} 

try: 

ba = sig.bind_partial(*partial_args, **partial_keywords) 

except TypeError as ex: 

msg = 'partial object {0!r} has incorrect arguments'.format(obj) 

raise ValueError(msg) 

 

for arg_name, arg_value in ba.arguments.items(): 

param = new_params[arg_name] 

if arg_name in partial_keywords: 

# We set a new default value, because the following code 

# is correct: 

# 

# >>> def foo(a): print(a) 

# >>> print(partial(partial(foo, a=10), a=20)()) 

# 20 

# >>> print(partial(partial(foo, a=10), a=20)(a=30)) 

# 30 

# 

# So, with 'partial' objects, passing a keyword argument is 

# like setting a new default value for the corresponding 

# parameter 

# 

# We also mark this parameter with '_partial_kwarg' 

# flag. Later, in '_bind', the 'default' value of this 

# parameter will be added to 'kwargs', to simulate 

# the 'functools.partial' real call. 

new_params[arg_name] = param.replace(default=arg_value, 

_partial_kwarg=True) 

 

elif (param.kind not in (_VAR_KEYWORD, _VAR_POSITIONAL) and 

not param._partial_kwarg): 

new_params.pop(arg_name) 

 

return sig.replace(parameters=new_params.values()) 

 

sig = None 

if isinstance(obj, type): 

# obj is a class or a metaclass 

 

# First, let's see if it has an overloaded __call__ defined 

# in its metaclass 

call = _get_user_defined_method(type(obj), '__call__') 

if call is not None: 

sig = signature(call) 

else: 

# Now we check if the 'obj' class has a '__new__' method 

new = _get_user_defined_method(obj, '__new__') 

if new is not None: 

sig = signature(new) 

else: 

# Finally, we should have at least __init__ implemented 

init = _get_user_defined_method(obj, '__init__') 

if init is not None: 

sig = signature(init) 

elif not isinstance(obj, _NonUserDefinedCallables): 

# An object with __call__ 

# We also check that the 'obj' is not an instance of 

# _WrapperDescriptor or _MethodWrapper to avoid 

# infinite recursion (and even potential segfault) 

call = _get_user_defined_method(type(obj), '__call__', 'im_func') 

if call is not None: 

sig = signature(call) 

 

if sig is not None: 

# For classes and objects we skip the first parameter of their 

# __call__, __new__, or __init__ methods 

return sig.replace(parameters=tuple(sig.parameters.values())[1:]) 

 

if isinstance(obj, types.BuiltinFunctionType): 

# Raise a nicer error message for builtins 

msg = 'no signature found for builtin function {0!r}'.format(obj) 

raise ValueError(msg) 

 

raise ValueError('callable {0!r} is not supported by signature'.format(obj)) 

 

 

class _void(object): 

'''A private marker - used in Parameter & Signature''' 

 

 

class _empty(object): 

pass 

 

 

class _ParameterKind(int): 

def __new__(self, *args, **kwargs): 

obj = int.__new__(self, *args) 

obj._name = kwargs['name'] 

return obj 

 

def __str__(self): 

return self._name 

 

def __repr__(self): 

return '<_ParameterKind: {0!r}>'.format(self._name) 

 

 

_POSITIONAL_ONLY = _ParameterKind(0, name='POSITIONAL_ONLY') 

_POSITIONAL_OR_KEYWORD = _ParameterKind(1, name='POSITIONAL_OR_KEYWORD') 

_VAR_POSITIONAL = _ParameterKind(2, name='VAR_POSITIONAL') 

_KEYWORD_ONLY = _ParameterKind(3, name='KEYWORD_ONLY') 

_VAR_KEYWORD = _ParameterKind(4, name='VAR_KEYWORD') 

 

 

class Parameter(object): 

'''Represents a parameter in a function signature. 

 

Has the following public attributes: 

 

* name : str 

The name of the parameter as a string. 

* default : object 

The default value for the parameter if specified. If the 

parameter has no default value, this attribute is not set. 

* annotation 

The annotation for the parameter if specified. If the 

parameter has no annotation, this attribute is not set. 

* kind : str 

Describes how argument values are bound to the parameter. 

Possible values: `Parameter.POSITIONAL_ONLY`, 

`Parameter.POSITIONAL_OR_KEYWORD`, `Parameter.VAR_POSITIONAL`, 

`Parameter.KEYWORD_ONLY`, `Parameter.VAR_KEYWORD`. 

''' 

 

__slots__ = ('_name', '_kind', '_default', '_annotation', '_partial_kwarg') 

 

POSITIONAL_ONLY = _POSITIONAL_ONLY 

POSITIONAL_OR_KEYWORD = _POSITIONAL_OR_KEYWORD 

VAR_POSITIONAL = _VAR_POSITIONAL 

KEYWORD_ONLY = _KEYWORD_ONLY 

VAR_KEYWORD = _VAR_KEYWORD 

 

empty = _empty 

 

def __init__(self, name, kind, default=_empty, annotation=_empty, 

_partial_kwarg=False): 

 

if kind not in (_POSITIONAL_ONLY, _POSITIONAL_OR_KEYWORD, 

_VAR_POSITIONAL, _KEYWORD_ONLY, _VAR_KEYWORD): 

raise ValueError("invalid value for 'Parameter.kind' attribute") 

self._kind = kind 

 

if default is not _empty: 

if kind in (_VAR_POSITIONAL, _VAR_KEYWORD): 

msg = '{0} parameters cannot have default values'.format(kind) 

raise ValueError(msg) 

self._default = default 

self._annotation = annotation 

 

if name is None: 

if kind != _POSITIONAL_ONLY: 

raise ValueError("None is not a valid name for a " 

"non-positional-only parameter") 

self._name = name 

else: 

name = str(name) 

if kind != _POSITIONAL_ONLY and not re.match(r'[a-z_]\w*$', name, re.I): 

msg = '{0!r} is not a valid parameter name'.format(name) 

raise ValueError(msg) 

self._name = name 

 

self._partial_kwarg = _partial_kwarg 

 

@property 

def name(self): 

return self._name 

 

@property 

def default(self): 

return self._default 

 

@property 

def annotation(self): 

return self._annotation 

 

@property 

def kind(self): 

return self._kind 

 

def replace(self, name=_void, kind=_void, annotation=_void, 

default=_void, _partial_kwarg=_void): 

'''Creates a customized copy of the Parameter.''' 

 

if name is _void: 

name = self._name 

 

if kind is _void: 

kind = self._kind 

 

if annotation is _void: 

annotation = self._annotation 

 

if default is _void: 

default = self._default 

 

if _partial_kwarg is _void: 

_partial_kwarg = self._partial_kwarg 

 

return type(self)(name, kind, default=default, annotation=annotation, 

_partial_kwarg=_partial_kwarg) 

 

def __str__(self): 

kind = self.kind 

 

formatted = self._name 

if kind == _POSITIONAL_ONLY: 

if formatted is None: 

formatted = '' 

formatted = '<{0}>'.format(formatted) 

 

# Add annotation and default value 

if self._annotation is not _empty: 

formatted = '{0}:{1}'.format(formatted, 

formatannotation(self._annotation)) 

 

if self._default is not _empty: 

formatted = '{0}={1}'.format(formatted, repr(self._default)) 

 

if kind == _VAR_POSITIONAL: 

formatted = '*' + formatted 

elif kind == _VAR_KEYWORD: 

formatted = '**' + formatted 

 

return formatted 

 

def __repr__(self): 

return '<{0} at {1:#x} {2!r}>'.format(self.__class__.__name__, 

id(self), self.name) 

 

def __hash__(self): 

msg = "unhashable type: '{0}'".format(self.__class__.__name__) 

raise TypeError(msg) 

 

def __eq__(self, other): 

return (issubclass(other.__class__, Parameter) and 

self._name == other._name and 

self._kind == other._kind and 

self._default == other._default and 

self._annotation == other._annotation) 

 

def __ne__(self, other): 

return not self.__eq__(other) 

 

 

class BoundArguments(object): 

'''Result of `Signature.bind` call. Holds the mapping of arguments 

to the function's parameters. 

 

Has the following public attributes: 

 

* arguments : OrderedDict 

An ordered mutable mapping of parameters' names to arguments' values. 

Does not contain arguments' default values. 

* signature : Signature 

The Signature object that created this instance. 

* args : tuple 

Tuple of positional arguments values. 

* kwargs : dict 

Dict of keyword arguments values. 

''' 

 

def __init__(self, signature, arguments): 

self.arguments = arguments 

self._signature = signature 

 

@property 

def signature(self): 

return self._signature 

 

@property 

def args(self): 

args = [] 

for param_name, param in self._signature.parameters.items(): 

if (param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY) or 

param._partial_kwarg): 

# Keyword arguments mapped by 'functools.partial' 

# (Parameter._partial_kwarg is True) are mapped 

# in 'BoundArguments.kwargs', along with VAR_KEYWORD & 

# KEYWORD_ONLY 

break 

 

try: 

arg = self.arguments[param_name] 

except KeyError: 

# We're done here. Other arguments 

# will be mapped in 'BoundArguments.kwargs' 

break 

else: 

if param.kind == _VAR_POSITIONAL: 

# *args 

args.extend(arg) 

else: 

# plain argument 

args.append(arg) 

 

return tuple(args) 

 

@property 

def kwargs(self): 

kwargs = {} 

kwargs_started = False 

for param_name, param in self._signature.parameters.items(): 

if not kwargs_started: 

if (param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY) or 

param._partial_kwarg): 

kwargs_started = True 

else: 

if param_name not in self.arguments: 

kwargs_started = True 

continue 

 

if not kwargs_started: 

continue 

 

try: 

arg = self.arguments[param_name] 

except KeyError: 

pass 

else: 

if param.kind == _VAR_KEYWORD: 

# **kwargs 

kwargs.update(arg) 

else: 

# plain keyword argument 

kwargs[param_name] = arg 

 

return kwargs 

 

def __hash__(self): 

msg = "unhashable type: '{0}'".format(self.__class__.__name__) 

raise TypeError(msg) 

 

def __eq__(self, other): 

return (issubclass(other.__class__, BoundArguments) and 

self.signature == other.signature and 

self.arguments == other.arguments) 

 

def __ne__(self, other): 

return not self.__eq__(other) 

 

 

class Signature(object): 

'''A Signature object represents the overall signature of a function. 

It stores a Parameter object for each parameter accepted by the 

function, as well as information specific to the function itself. 

 

A Signature object has the following public attributes and methods: 

 

* parameters : OrderedDict 

An ordered mapping of parameters' names to the corresponding 

Parameter objects (keyword-only arguments are in the same order 

as listed in `code.co_varnames`). 

* return_annotation : object 

The annotation for the return type of the function if specified. 

If the function has no annotation for its return type, this 

attribute is not set. 

* bind(*args, **kwargs) -> BoundArguments 

Creates a mapping from positional and keyword arguments to 

parameters. 

* bind_partial(*args, **kwargs) -> BoundArguments 

Creates a partial mapping from positional and keyword arguments 

to parameters (simulating 'functools.partial' behavior.) 

''' 

 

__slots__ = ('_return_annotation', '_parameters') 

 

_parameter_cls = Parameter 

_bound_arguments_cls = BoundArguments 

 

empty = _empty 

 

def __init__(self, parameters=None, return_annotation=_empty, 

__validate_parameters__=True): 

'''Constructs Signature from the given list of Parameter 

objects and 'return_annotation'. All arguments are optional. 

''' 

 

if parameters is None: 

params = OrderedDict() 

else: 

if __validate_parameters__: 

params = OrderedDict() 

top_kind = _POSITIONAL_ONLY 

 

for idx, param in enumerate(parameters): 

kind = param.kind 

if kind < top_kind: 

msg = 'wrong parameter order: {0} before {1}' 

msg = msg.format(top_kind, param.kind) 

raise ValueError(msg) 

else: 

top_kind = kind 

 

name = param.name 

if name is None: 

name = str(idx) 

param = param.replace(name=name) 

 

if name in params: 

msg = 'duplicate parameter name: {0!r}'.format(name) 

raise ValueError(msg) 

params[name] = param 

else: 

params = OrderedDict(((param.name, param) 

for param in parameters)) 

 

self._parameters = params 

self._return_annotation = return_annotation 

 

@classmethod 

def from_function(cls, func): 

'''Constructs Signature for the given python function''' 

 

if not isinstance(func, types.FunctionType): 

raise TypeError('{0!r} is not a Python function'.format(func)) 

 

Parameter = cls._parameter_cls 

 

# Parameter information. 

func_code = func.__code__ 

pos_count = func_code.co_argcount 

arg_names = func_code.co_varnames 

positional = tuple(arg_names[:pos_count]) 

keyword_only_count = getattr(func_code, 'co_kwonlyargcount', 0) 

keyword_only = arg_names[pos_count:(pos_count + keyword_only_count)] 

annotations = getattr(func, '__annotations__', {}) 

defaults = func.__defaults__ 

kwdefaults = getattr(func, '__kwdefaults__', None) 

 

if defaults: 

pos_default_count = len(defaults) 

else: 

pos_default_count = 0 

 

parameters = [] 

 

# Non-keyword-only parameters w/o defaults. 

non_default_count = pos_count - pos_default_count 

for name in positional[:non_default_count]: 

annotation = annotations.get(name, _empty) 

parameters.append(Parameter(name, annotation=annotation, 

kind=_POSITIONAL_OR_KEYWORD)) 

 

# ... w/ defaults. 

for offset, name in enumerate(positional[non_default_count:]): 

annotation = annotations.get(name, _empty) 

parameters.append(Parameter(name, annotation=annotation, 

kind=_POSITIONAL_OR_KEYWORD, 

default=defaults[offset])) 

 

# *args 

if func_code.co_flags & 0x04: 

name = arg_names[pos_count + keyword_only_count] 

annotation = annotations.get(name, _empty) 

parameters.append(Parameter(name, annotation=annotation, 

kind=_VAR_POSITIONAL)) 

 

# Keyword-only parameters. 

for name in keyword_only: 

default = _empty 

if kwdefaults is not None: 

default = kwdefaults.get(name, _empty) 

 

annotation = annotations.get(name, _empty) 

parameters.append(Parameter(name, annotation=annotation, 

kind=_KEYWORD_ONLY, 

default=default)) 

# **kwargs 

if func_code.co_flags & 0x08: 

index = pos_count + keyword_only_count 

if func_code.co_flags & 0x04: 

index += 1 

 

name = arg_names[index] 

annotation = annotations.get(name, _empty) 

parameters.append(Parameter(name, annotation=annotation, 

kind=_VAR_KEYWORD)) 

 

return cls(parameters, 

return_annotation=annotations.get('return', _empty), 

__validate_parameters__=False) 

 

@property 

def parameters(self): 

try: 

return types.MappingProxyType(self._parameters) 

except AttributeError: 

return OrderedDict(self._parameters.items()) 

 

@property 

def return_annotation(self): 

return self._return_annotation 

 

def replace(self, parameters=_void, return_annotation=_void): 

'''Creates a customized copy of the Signature. 

Pass 'parameters' and/or 'return_annotation' arguments 

to override them in the new copy. 

''' 

 

if parameters is _void: 

parameters = self.parameters.values() 

 

if return_annotation is _void: 

return_annotation = self._return_annotation 

 

return type(self)(parameters, 

return_annotation=return_annotation) 

 

def __hash__(self): 

msg = "unhashable type: '{0}'".format(self.__class__.__name__) 

raise TypeError(msg) 

 

def __eq__(self, other): 

if (not issubclass(type(other), Signature) or 

self.return_annotation != other.return_annotation or 

len(self.parameters) != len(other.parameters)): 

return False 

 

other_positions = dict((param, idx) 

for idx, param in enumerate(other.parameters.keys())) 

 

for idx, (param_name, param) in enumerate(self.parameters.items()): 

if param.kind == _KEYWORD_ONLY: 

try: 

other_param = other.parameters[param_name] 

except KeyError: 

return False 

else: 

if param != other_param: 

return False 

else: 

try: 

other_idx = other_positions[param_name] 

except KeyError: 

return False 

else: 

if (idx != other_idx or 

param != other.parameters[param_name]): 

return False 

 

return True 

 

def __ne__(self, other): 

return not self.__eq__(other) 

 

def _bind(self, args, kwargs, partial=False): 

'''Private method. Don't use directly.''' 

 

arguments = OrderedDict() 

 

parameters = iter(self.parameters.values()) 

parameters_ex = () 

arg_vals = iter(args) 

 

if partial: 

# Support for binding arguments to 'functools.partial' objects. 

# See 'functools.partial' case in 'signature()' implementation 

# for details. 

for param_name, param in self.parameters.items(): 

if (param._partial_kwarg and param_name not in kwargs): 

# Simulating 'functools.partial' behavior 

kwargs[param_name] = param.default 

 

while True: 

# Let's iterate through the positional arguments and corresponding 

# parameters 

try: 

arg_val = next(arg_vals) 

except StopIteration: 

# No more positional arguments 

try: 

param = next(parameters) 

except StopIteration: 

# No more parameters. That's it. Just need to check that 

# we have no `kwargs` after this while loop 

break 

else: 

if param.kind == _VAR_POSITIONAL: 

# That's OK, just empty *args. Let's start parsing 

# kwargs 

break 

elif param.name in kwargs: 

if param.kind == _POSITIONAL_ONLY: 

msg = '{arg!r} parameter is positional only, ' \ 

'but was passed as a keyword' 

msg = msg.format(arg=param.name) 

raise TypeError(msg) 

parameters_ex = (param,) 

break 

elif (param.kind == _VAR_KEYWORD or 

param.default is not _empty): 

# That's fine too - we have a default value for this 

# parameter. So, lets start parsing `kwargs`, starting 

# with the current parameter 

parameters_ex = (param,) 

break 

else: 

if partial: 

parameters_ex = (param,) 

break 

else: 

msg = '{arg!r} parameter lacking default value' 

msg = msg.format(arg=param.name) 

raise TypeError(msg) 

else: 

# We have a positional argument to process 

try: 

param = next(parameters) 

except StopIteration: 

raise TypeError('too many positional arguments') 

else: 

if param.kind in (_VAR_KEYWORD, _KEYWORD_ONLY): 

# Looks like we have no parameter for this positional 

# argument 

raise TypeError('too many positional arguments') 

 

if param.kind == _VAR_POSITIONAL: 

# We have an '*args'-like argument, let's fill it with 

# all positional arguments we have left and move on to 

# the next phase 

values = [arg_val] 

values.extend(arg_vals) 

arguments[param.name] = tuple(values) 

break 

 

if param.name in kwargs: 

raise TypeError('multiple values for argument ' 

'{arg!r}'.format(arg=param.name)) 

 

arguments[param.name] = arg_val 

 

# Now, we iterate through the remaining parameters to process 

# keyword arguments 

kwargs_param = None 

for param in itertools.chain(parameters_ex, parameters): 

if param.kind == _POSITIONAL_ONLY: 

# This should never happen in case of a properly built 

# Signature object (but let's have this check here 

# to ensure correct behaviour just in case) 

raise TypeError('{arg!r} parameter is positional only, ' 

'but was passed as a keyword'. \ 

format(arg=param.name)) 

 

if param.kind == _VAR_KEYWORD: 

# Memorize that we have a '**kwargs'-like parameter 

kwargs_param = param 

continue 

 

param_name = param.name 

try: 

arg_val = kwargs.pop(param_name) 

except KeyError: 

# We have no value for this parameter. It's fine though, 

# if it has a default value, or it is an '*args'-like 

# parameter, left alone by the processing of positional 

# arguments. 

if (not partial and param.kind != _VAR_POSITIONAL and 

param.default is _empty): 

raise TypeError('{arg!r} parameter lacking default value'. \ 

format(arg=param_name)) 

 

else: 

arguments[param_name] = arg_val 

 

if kwargs: 

if kwargs_param is not None: 

# Process our '**kwargs'-like parameter 

arguments[kwargs_param.name] = kwargs 

else: 

raise TypeError('too many keyword arguments %r' % kwargs) 

 

return self._bound_arguments_cls(self, arguments) 

 

def bind(*args, **kwargs): 

'''Get a BoundArguments object, that maps the passed `args` 

and `kwargs` to the function's signature. Raises `TypeError` 

if the passed arguments can not be bound. 

''' 

return args[0]._bind(args[1:], kwargs) 

 

def bind_partial(self, *args, **kwargs): 

'''Get a BoundArguments object, that partially maps the 

passed `args` and `kwargs` to the function's signature. 

Raises `TypeError` if the passed arguments can not be bound. 

''' 

return self._bind(args, kwargs, partial=True) 

 

def __str__(self): 

result = [] 

render_kw_only_separator = True 

for idx, param in enumerate(self.parameters.values()): 

formatted = str(param) 

 

kind = param.kind 

if kind == _VAR_POSITIONAL: 

# OK, we have an '*args'-like parameter, so we won't need 

# a '*' to separate keyword-only arguments 

render_kw_only_separator = False 

elif kind == _KEYWORD_ONLY and render_kw_only_separator: 

# We have a keyword-only parameter to render and we haven't 

# rendered an '*args'-like parameter before, so add a '*' 

# separator to the parameters list ("foo(arg1, *, arg2)" case) 

result.append('*') 

# This condition should be only triggered once, so 

# reset the flag 

render_kw_only_separator = False 

 

result.append(formatted) 

 

rendered = '({0})'.format(', '.join(result)) 

 

if self.return_annotation is not _empty: 

anno = formatannotation(self.return_annotation) 

rendered += ' -> {0}'.format(anno) 

 

return rendered