code: def test_cull():
      a = {"x": 1, "y": (inc, "x")}
      hg = HighLevelGraph({"a": a}, {"a": set()})
  
      culled_by_x = hg.cull({"x"})
      assert dict(culled_by_x) == {"x": 1}
  
      # parameter is the raw output of __dask_keys__()
      culled_by_y = hg.cull([[["y"]]])
      assert dict(culled_by_y) == a
  
imports: from __future__ import annotations
  import os
  import threading
  import xml.etree.ElementTree
  from collections.abc import Set
  from concurrent.futures import ThreadPoolExecutor
  import pytest
  import dask
  from dask.blockwise import Blockwise, blockwise_token
  from dask.highlevelgraph import HighLevelGraph, Layer, MaterializedLayer, to_graphviz
  from dask.utils_test import inc
label_desc: Use image node_id 6 for calling a global function with example usage: test_cull() without return types