Reference static class method in gin config

In the following example I would like to assign a parameter to the static method ImplClass.foo . The reference `@ImplClass.foo` is not being resolved properly by gin.

```
from abc import ABC, abstractmethod
import gin

class BaseClass(ABC):
@staticmethod
@abstractmethod
def foo(a):
pass

@gin.register()
class ImplClass(BaseClass):
@gin.register()
def foo(a):
print("hello")
```