code: def test_as_completed_is_empty(client):
      ac = as_completed()
      assert ac.is_empty()
      x = client.submit(inc, 1)
      ac.add(x)
      assert not ac.is_empty()
      assert next(ac) is x
      assert ac.is_empty()
  
imports: from __future__ import annotations
  import asyncio
  import queue
  import random
  from collections.abc import Iterator
  from operator import add
  from time import sleep
  import pytest
  from distributed import TimeoutError
  from distributed.client import _as_completed, _first_completed, as_completed, wait
  from distributed.metrics import time
  from distributed.utils import CancelledError
  from distributed.utils_test import gen_cluster, inc, slowinc, throws
label_desc: Use image node_id 7 for calling a global function with example usage: test_as_completed_is_empty(client) without return types