code: def FindFieldByName(self, full_name):
      
      full_name = _NormalizeFullyQualifiedName(full_name)
      message_name, _, field_name = full_name.rpartition('.')
      message_descriptor = self.FindMessageTypeByName(message_name)
      return message_descriptor.fields_by_name[field_name]
docs: Loads the named field descriptor from the pool.
  
      Args:
        full_name: The full name of the field descriptor to load.
  
      Returns:
        The field descriptor for the named field.
  
      Raises:
        KeyError: if the field cannot be found in the pool.