code: def reset(self, name):
          
          message_type = type(self)
          try:
              field = message_type.field_by_name(name)
          except KeyError:
              if name not in message_type.__by_name:
                  raise AttributeError('Message %s has no field %s' % (
                      message_type.__name__, name))
          if field.repeated:
              self.__tags[field.number] = FieldList(field, [])
          else:
              self.__tags.pop(field.number, None)
docs: Reset assigned value for field.
  
          Resetting a field will return it to its default value or None.
  
          Args:
            name: Name of field to reset.