code: def test_groups():
      many_to_one = dict(zip("abcde", [0, 0, 1, 1, 2]))
      actual = groups(many_to_one)
      expected = {0: {"a", "b"}, 1: {"c", "d"}, 2: {"e"}}
      assert actual == expected
      assert {} == groups({})
  
imports: import random
  from copy import copy
  import pytest
  import networkx
  from networkx.utils import PythonRandomInterface, arbitrary_element, create_py_random_state, create_random_state, dict_to_numpy_array, discrete_sequence, flatten, groups, make_list_of_ints, pairwise, powerlaw_sequence
  from networkx.utils.misc import _dict_to_numpy_array1, _dict_to_numpy_array2
label_desc: Use image node_id 5 for calling a global function with example usage: test_groups() without return types