docs: def handler(self, scheme_name=None):
  		""" Return handler which scheme name matches the specified one
  
  		:param scheme_name: scheme name to search for
  		:return: WSchemeHandler class or None (if matching handler was not found)
  		"""
  		if scheme_name is None:
  			return self.__default_handler_cls
  		for handler in self.__handlers_cls:
  			if handler.scheme_specification().scheme_name() == scheme_name:
  				return handler