dbname (str) - Optional db identifier. Used for informational purposes. If
omitted or None, the information just won't be emitted.
types (callable) - Extra type loader. If the type reflection fails, because
SQLAlchemy cannot resolve it, the type loader will be called with
the type name, (bound) metadata and the symbol table. It is
responsible for modifying the symbols and imports and the
dialect's ischema_names. If omitted or None, the reflector
will always fail on unknown types.