code: def test_turn_off_fusion():
      x = da.ones(10, chunks=(5,))
      y = da.sum(x + 1 + 2 + 3)
  
      a = y.__dask_optimize__(y.dask, y.__dask_keys__())
  
      with dask.config.set({"optimization.fuse.ave-width": 0}):
          b = y.__dask_optimize__(y.dask, y.__dask_keys__())
  
      assert dask.get(a, y.__dask_keys__()) == dask.get(
          b, y.__dask_keys__()
      )
      assert len(a) < len(b)
  
imports: from __future__ import annotations
  import pytest
  import numpy
  import dask
  import dask.array
  from dask.array.chunk import getitem
  from dask.array.core import getter
  from dask.array.core import getter_nofancy
  from dask.array.optimization import _is_getter_task, fuse_slice, optimize, optimize_blockwise, optimize_slices
  from dask.array.utils import assert_eq
  from dask.highlevelgraph import HighLevelGraph
  from dask.optimization import SubgraphCallable, fuse
  from dask.utils import SerializableLock
label_desc: Use image node_id 21 for calling a global function with example usage: test_turn_off_fusion() without return types