How do I cleanly test equality of objects in Mypy without producing errors?

I have the following function:

import pandas as pd

def eq(left: pd.Timestamp, right: pd.Timestamp) -> bool:
    return left == right

I get the following error when I run it through Mypy:

error: Returning Any from function declared to return "bool"

I believe this is because Mypy doesn't know about pd.Timestamp so treats it as Any. (Using the Mypy reveal_type function shows that Mypy treats left and right as Any.)

What is the correct way to deal with this to stop Mypy complaining?

from How do I cleanly test equality of objects in Mypy without producing errors?