docs: def held(self, sname):
          """
          Determines whether a button is currently held, identifying it by standard name
  
          :param sname:
              The standard name of the button
          :return:
              None if the button is not held down, or is not available, otherwise the number of seconds as a floating
              point value since it was pressed
          """
          state = self.buttons_by_sname.get(sname)
          if state is not None:
              if state.is_pressed and state.last_pressed is not None:
                  return time() - state.last_pressed
          return None