code: def start(self):
          
          msg = ''
          if not self.running():
              if self._port == 0:
                  self._port = _port_not_in_use()
              self._process = start_server_background(self._port)
          else:
              msg = 'Server already started\n'
          msg += 'Server running at {}'.format(self.url())
          print(msg)
docs: Start server if not previously started.