docs: def __args_check(self, envelope, target, modification_code):
  		""" Method checks arguments, that are specified to the
  		:meth:`.WMessengerFixedModificationLayer.encode` and :meth:`.WMessengerFixedModificationLayer.decode`
  		methods
  
  		:param envelope: same as envelope in :meth:`.WMessengerFixedModificationLayer.encode` and \
  		:meth:`.WMessengerFixedModificationLayer.decode` methods
  		:param target: same as target in :meth:`.WMessengerFixedModificationLayer.encode` and \
  		:meth:`.WMessengerFixedModificationLayer.decode` methods
  		:param modification_code: same as modification_code in \
  		:meth:`.WMessengerFixedModificationLayer.encode` and :meth:`.WMessengerFixedModificationLayer.decode` \
  		methods
  
  		:return: None
  		"""
  		if target is None:
  			raise RuntimeError('"target" argument must be specified for this layer')
  		if modification_code is None:
  			raise RuntimeError('"modification_code" argument must be specified for this layer')
  
  		if isinstance(target, WMessengerFixedModificationLayer.Target) is False:
  			raise TypeError('Invalid "target" argument')
  
  		if isinstance(envelope, WMessengerTextEnvelope) is True:
  			if isinstance(modification_code, str) is False:
  				raise TypeError('Invalid "modification_code" argument for specified envelope')
  		elif isinstance(modification_code, bytes) is False:
  			raise TypeError('Invalid "modification_code" argument for specified envelope')