How to use __getitem__ on a class while keep typing/mypy happy

I am modelling a problem where it doesn't make sense to have instantations of a class -- in this case the periodic table. I want to be able to index the periodic table with an int and get the associated element (from the atomic number; the element objects are stored as class variables). I can do this easily with metaclasses, but mypy doesn't like this. Here is my approach:

class PeriodicTableBase(type):
    def __getitem__(cls, x: int) -> int:
        return x

class PeriodicTable(metaclass=PeriodicTableBase):
    pass

a = PeriodicTable[1]

and after finding PEP560:

class PeriodicTable:
    def __class_getitem__(cls, x: int) -> int:
        return x

a = PeriodicTable[1]

Mypy gives the same error for both of these (presumably because they collide with the way generic types are defined):

Typing.py:9: error: "PeriodicTable" expects no type arguments, but 1 given
Typing.py:9: error: Invalid type: try using Literal[1] instead?

Of course they both function at runtime.

Is there a way I can do this cleanly whilst keeping mypy happy?