The documentation (https://docs.python.org/3/library/functions.html#type) shows type's signature as:

class type(object)
class type(name, bases, dict)


But the "actual" 2nd signature in CPython 3.6+ is:

class type(name, bases, dict, **kwargs)


**kwargs here gets passed to __init_subclass__ in the same way that keywords in a class statement do so that:

type("Bar", (Foo,), {}, spam='ham')

is equivalent to

class Bar(Foo, spam='ham'): pass


It's not clear to me whether this is behavior to rely on. I started using this intuitively, but found that my type checker reasonably complained.

Looking through the commit that implemented PEP 487 (d78448e9), it seems this may have been incidental. Additionally I haven't found mention of this in PEP 487 or the documentation and I can't seem to find any tests for it.