docs: def clean_value(self):
          '''
          Current field's converted value from form's python_data.
          '''
          # XXX cached_property is used only for set initial state
          #     this property should be set every time field data
          #     has been changed, for instance, in accept method
          python_data = self.parent.python_data
          if self.name in python_data:
              return python_data[self.name]
          return self.get_initial()