I changed the annotation for the axis argument to stack from Optional[int] to just int, since the default is 0 rather than None. However, I'm not sure if this should be done, so I can revert it if we think the Optional is better. It's worth noting that np.stack(axis=None) gives an error.

I also changed the endpoint argument of linspace to be bool instead of Optional[bool]. Perhaps there was just some confusion about the difference between Optional[x], which is a shorthand for Union[x, None] (see https://docs.python.org/3/library/typing.html#typing.Optional), and keyword-only arguments with default values, which may be None or something else.

Perhaps there was just some confusion about the difference between Optional[x].

No. Just a copy and paste error.