Return a json dictionary representing this model.

def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self, 'prompt') and self.prompt is not None:
            _dict['prompt'] = self.prompt
        if hasattr(self, 'none_of_the_above_prompt'
                  ) and self.none_of_the_above_prompt is not None:
            _dict['none_of_the_above_prompt'] = self.none_of_the_above_prompt
        if hasattr(self, 'enabled') and self.enabled is not None:
            _dict['enabled'] = self.enabled
        if hasattr(self, 'sensitivity') and self.sensitivity is not None:
            _dict['sensitivity'] = self.sensitivity
        return _dict