code: def test_combinations():
      actual = list(combinations("ABCD", 2))
      desired = [
          ("A", "B"),
          ("A", "C"),
          ("A", "D"),
          ("B", "C"),
          ("B", "D"),
          ("C", "D"),
      ]
      assert_(
          actual == desired,
          "{!r} not equal {!r}".format(actual, desired),
      )
  
      actual = list(combinations(lrange(4), 3))
      desired = [(0, 1, 2), (0, 1, 3), (0, 2, 3), (1, 2, 3)]
      assert_(
          actual == desired,
          "{!r} not equal {!r}".format(actual, desired),
      )
  
imports: from statsmodels.compat import lrange
  from itertools import combinations, zip_longest
  from numpy.testing import assert_
label_desc: Use image node_id 2 for calling a global function with example usage: test_combinations() without return types