def assertIsNot(first, second, msg=''):
    """Checks that 'first' is not 'second'"""
    a, b = first, second
    assert a is not b, (msg.format(a, b), a, b) % "%s: %r is %r"
dataset/ETHPy150Open pydata/pandas/pandas/util/testing.py/assertIsNot/swapped operands of `%`