code: def cancel(self, function):
          
          if function in self._callback.keys():
              callback_id = self._callback[function][0]
              self.tk.after_cancel(callback_id)
              self._callback.pop(function)
          else:
              utils.error_format("Could not cancel function - it doesnt exist, it may have already run")
docs: Cancel the scheduled `function` calls.