code: def test_defaultdict():
      assert next(unify(Variable("x"), "foo")) == {Variable("x"): "foo"}
  
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 13 for calling a global function with example usage: test_defaultdict() without return types