Weather HAT library wind speed error?

Hi - I’m new to RPi and python coding, and for my first project I have a Pimoroni Weather HAT with the rain and wind sensors. All seems to be running ok, but I can’t get “wind average” working.
Error message shows line 90 of weatherhat library file “” as follows:
“return self.cms_to_mph(self.average(sample_over))”
… but there is no definition in the file for “cms_to_mph”.
Is this an error in line 90? If so it probably also applies to line 87. (Should they read “ms_to_mph”?)
… or am I missing something (which is quite possible as I’m a newbie feeling my way around this!)
Thanks for any help.