Clears the deque if certain parts of the config have changed.

def _maybe_clear_deque(self):
    '''Clears the deque if certain parts of the config have changed.'''

    for config_item in ['values', 'mode', 'show_all']:
      if self.config[config_item] != self.old_config[config_item]:
        self.sections_over_time.clear()
        break

    self.old_config = self.config

    window_size = self.config['window_size']
    if window_size != self.sections_over_time.maxlen:
      self.sections_over_time = deque(self.sections_over_time, window_size)