code: def test_commutativity():
      c1 = Compound("CAdd", (a, b))
      c2 = Compound("CAdd", (x, y))
      assert is_commutative(c1) and is_commutative(c2)
      assert len(list(unify(c1, c2, {}))) == 2
  
file_path: sympy/sympy/unify/tests/test_unify.py
imports: from sympy.unify.core import Compound, Variable, CondVariable, allcombinations
  from sympy.unify import core
label_desc: Use image node_id 11 for calling a global function with example usage: test_commutativity() without return types