def with_metaclass(meta, *bases):
    """Create a base class with a metaclass."""
    # This requires a bit of explanation: the basic idea is to make a dummy
    # metaclass for one level of class instantiation that replaces itself with
    # the actual metaclass.
    class Metaclass(meta):
        def __new__(cls, name, this_bases, d):
            return meta(name, bases, d)
    return type.__new__(Metaclass, str('temporary_class'), (), {})
Create a base class with a metaclass.