Calling spy() now fills args and kwargs with empty tuple or dictionary

[jonathan-benn]

The next fixes will build on top of this one

[note35]

About the following steps, if you are not familiar about git, here are some tips. (If you knew them before, please ignore them.)

• You can directly modify your local branch based on those reviews. And after you push to your branch, it will immediately happen in this PR.
• Instead of git push, you can use force push to make your commits cleaner (option). In this case, since you only have one commit, you can use git add xxx and git commit --amend in your local branch, and use git push origin <your_branch_name> --force to update remote branch.
• Instead of general commit, I highly recommend add those indicators. (option)

[note35]

LGTM