code: def test_get_dependencies_task_none():
      # Regression test for https://github.com/dask/distributed/issues/2756
      dsk = {"foo": None}
      assert get_dependencies(dsk, task=dsk["foo"]) == set()
  
imports: from __future__ import annotations
  import pickle
  from collections import namedtuple
  import pytest
  from dask.core import flatten, get, get_dependencies, get_deps, getcycle, has_tasks, ishashable, iskey, istask, literal, preorder_traversal, quote, subs, validate_key
  from dask.utils_test import GetFunctionTestMixin, add, inc
label_desc: Use image node_id 16 for calling a global function with example usage: test_get_dependencies_task_none() without return types