class M2(type):

def __prepare__(name, bases, **kwargs):

assert name == "C"

assert bases == ()

assert kwargs["x"] == 5

assert "metaclass" not in kwargs

return {"a": 1}

def __new__(cls, name, bases, classdict, **kwargs):

assert cls == M2

assert name == "C"

assert bases == ()

assert kwargs["x"] == 5

assert classdict["a"] == 1

classdict["b"] = 2

return type.__new__(cls, name, bases, classdict)

def __init__(self, name, bases, classdict, **kwargs):

assert name == "C"

assert bases == ()

assert classdict["a"] == 1

assert classdict["b"] == 2

self.c = 3

assert kwargs["x"] == 5

class C(metaclass=M2, x=5): pass

assert C.c == 3