def __init__(self, op, operand):
        super(UnaryOp, self).__init__(op, (operand,))
        self.operand = operand

        try:
            self.func = _unary_ops_dict[op]
        except __HOLE__:
            raise ValueError('Invalid unary operator {0!r}, valid operators '
                             'are {1}'.format(op, _unary_ops_syms))
dataset/ETHPy150Open pydata/pandas/pandas/computation/ops.py/UnaryOp.__init__