See #20338 for why I think 70 (or even 79, the limit in CallTipWindow) is too low a limit.

The purpose of grabbing multiple lines is to get the signature lines of builtins. I believe the max number of lines needed is 5, for bytes. however, identifying likely builtins by the absence of a signature from inspect, which works now, will not work when Clinic and inspect start giving us such. Even when if Clinic produces a signature string for bytes, it will probably be opaque and the doc lines would still be helpful. So I think we can try up to 5 lines from the docstring for any object. I am working on a revision of the patch.