code: def transform(self, pyobject):
          
          if pyobject is None:
              return ('none',)
          object_type = type(pyobject)
          try:
              method = getattr(self, object_type.__name__ + '_to_textual')
              return method(pyobject)
          except AttributeError:
              return ('unknown',)
docs: Transform a `PyObject` to textual form