def generic_is_not(context, builder, sig, args):
    """
    Implement `x is not y` as `not (x is y)`.
    """
    is_impl = context.get_function(operator.is_, sig)
    return builder.not_(is_impl(builder, args))

    Implement `x is not y` as `not (x is y)`.
    
numba/cpython/new_builtins.py