def __new__(cls):
    """
        Return the cls itself.  This makes both equality and identity True for comparing the class
        to an instance of the class, preventing common usage errors.

        Preferred usage::

            a = Sentinel
            if a is Sentinel:
                print('Sentinel value')

        However, these are True as well, eliminating common usage errors::

            if Sentinel is Sentinel():
                print('Sentinel value')

            if Sentinel == Sentinel():
                print('Sentinel value')
        """
    return cls
