Return a json dictionary representing this model.

def _to_dict(self):
        """Return a json dictionary representing this model."""
        _dict = {}
        if hasattr(self, 'type') and self.type is not None:
            _dict['type'] = self.type
        if hasattr(self, 'credential_id') and self.credential_id is not None:
            _dict['credential_id'] = self.credential_id
        if hasattr(self, 'schedule') and self.schedule is not None:
            _dict['schedule'] = self.schedule._to_dict()
        if hasattr(self, 'options') and self.options is not None:
            _dict['options'] = self.options._to_dict()
        return _dict