def to_dict(self):
        """Return the resource as a dictionary.

        :rtype: dict
        """
        result_dict = {}
        for column in self.__table__.columns.keys():  # pylint: disable=no-member
            value = result_dict[column] = getattr(self, column, None)
            if isinstance(value, Decimal):
                result_dict[column] = float(result_dict[column])
            elif isinstance(value, datetime.datetime):
                result_dict[column] = value.isoformat()
        return result_dict
Return the resource as a dictionary.

        :rtype: dict