https://nianticlabs.com/terms/
3.1 Cheating
Niantic prohibits cheating, and we constantly take steps to improve our anti-cheat measures. Cheating includes any action that attempts to or actually alters or interferes with the normal behavior or rules of a Service. Cheating includes, but is not limited to, any of the following behavior, on your own behalf or on behalf of others:
Accessing Services in an unauthorized manner (including using modified or unofficial third party software);
Playing with multiple accounts for the same Service;
Sharing accounts;
Using any techniques to alter or falsify a device’s location (for example through GPS spoofing); and/or
Selling or trading accounts.