def _get_dev_port(backend, instance=None):
 port = os.environ.get(_get_dev_port_var(backend, instance), None)
 if port:
  return int(port)
 else:
  return None

def _get_dev_port ( backend , instance = None ) : port = os . environ . get ( _get_dev_port_var ( backend , instance ) , None ) if port : return int ( port ) else : return None
returns the port for a backend [instance] in the dev_appserver .