code: def test_subs():
      from sympy.core.symbol import symbols
  
      a, b, c, d, e, f = symbols("a,b,c,d,e,f")
      mapping = {a: d, d: a, Basic(e): Basic(f)}
      expr = Basic(a, Basic(b, c), Basic(d, Basic(e)))
      result = Basic(d, Basic(b, c), Basic(a, Basic(f)))
      assert subs(mapping)(expr) == result
  
imports: from sympy.strategies.tools import subs, typed
  from sympy.strategies.rl import rm_id
  from sympy.core.basic import Basic
  from sympy.core.singleton import S
label_desc: Use image node_id 1 for calling a global function with example usage: test_subs() without return types