code: def _current_web_port(self):
          
          info = inspect_container(self._get_container_name('web'))
          if info is None:
              return None
          try:
              if not info['State']['Running']:
                  return None
              return info['NetworkSettings']['Ports']['5000/tcp'][0]['HostPort']
          except TypeError:
              return None
docs: return just the port number for the web container, or None if
          not running