def __init__(self, precision='seconds', error=None, **kwargs):
        precision = precision.lower()
        units = (self.DAYS, self.SECONDS, self.MICROSECONDS)

        if units not in precision:
            msg = 'The precision must be "{0}", "{1}" or "{2}".'.format(*units)
            raise ValueError(msg)

        self.precision = precision
        super(TimeDelta, self).__init__(error=error, **kwargs)
dataset/ETHPy150Open marshmallow-code/marshmallow/marshmallow/fields.py/TimeDelta.__init__/swapped operands of `not in`