Error with methods defined as function references wrapped in staticmethod() 

```py
def foo(key: str) -> str:
	return key


class A:
	@staticmethod
	def foobar(key: str) -> str:
		return "hello world"


class B(A):
	foobar = staticmethod(foo)
```

This yields the following error on B.foobar:

> error:Incompatible types in assignment (expression has type "staticmethod", base class "A" defined the type as "Callable[[str], str]")
