docs: def _to_dict(self):
          """Return a json dictionary representing this model."""
          _dict = {}
          if hasattr(self, 'anger') and self.anger is not None:
              _dict['anger'] = self.anger
          if hasattr(self, 'disgust') and self.disgust is not None:
              _dict['disgust'] = self.disgust
          if hasattr(self, 'fear') and self.fear is not None:
              _dict['fear'] = self.fear
          if hasattr(self, 'joy') and self.joy is not None:
              _dict['joy'] = self.joy
          if hasattr(self, 'sadness') and self.sadness is not None:
              _dict['sadness'] = self.sadness
          return _dict