def _set_dev_port(port, backend, instance=None, env=os.environ):
 env[_get_dev_port_var(backend, instance)] = str(port)

def _set_dev_port ( port , backend , instance = None , env = os . environ ) : env [ _get_dev_port_var ( backend , instance ) ] = str ( port )
sets the port for a backend [instance] in the dev_appserver .