Return a json dictionary representing this model.

def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self, 'name') and self.name is not None:
            _dict['name'] = self.name
        if hasattr(self, 'action_type') and self.action_type is not None:
            _dict['type'] = self.action_type
        if hasattr(self, 'parameters') and self.parameters is not None:
            _dict['parameters'] = self.parameters
        if hasattr(self,
                   'result_variable') and self.result_variable is not None:
            _dict['result_variable'] = self.result_variable
        if hasattr(self, 'credentials') and self.credentials is not None:
            _dict['credentials'] = self.credentials
        return _dict