可平仓数量

        Returns:
            [type] -- [description]

def close_available(self):
        """可平仓数量

        Returns:
            [type] -- [description]
        """
        return {
            'volume_long': self.volume_long - self.volume_long_frozen,
            'volume_short': self.volume_short - self.volume_short_frozen
        }