code: def serialize(self, node: SchemaNode,
                    value: Any) -> Union[str, ColanderNullType]:
          
          if value is None:
              retval = ''
          else:
              # noinspection PyUnresolvedReferences
              retval = self.type_.serialize(node, value)
          # log.debug("AllowNoneType.serialize: {!r} -> {!r}", value, retval)
          return retval
docs: Serializes Python object to string representation.