code: def test_top_down_easy():
      expr = Basic(S(1), S(2))
      expected = Basic(S(2), S(3))
      brl = top_down(inc)
  
      assert set(brl(expr)) == {expected}
  
file_path: sympy/sympy/strategies/branch/tests/test_traverse.py
imports: from sympy.core.basic import Basic
  from sympy.core.numbers import Integer
  from sympy.core.singleton import S
  from sympy.strategies.branch.traverse import top_down, sall
  from sympy.strategies.branch.core import do_one, identity
label_desc: Use image node_id 2 for calling a global function with example usage: test_top_down_easy() without return types