x.__init__(...) initializes x; see help(type(x)) for signature
Similar to set_key(...), but this instead checks if there is an existing keycode by the specified name, and associates the specified key combination to that name in addition. This way, if different browsers don’t catch one keycode, multiple keycodes can be assigned to the same test.
The code and a hash of the code is returned.
This the output of this function is cached so that it only needs to be generated once.