code: def test_subexpression_postprocessors():
      # The postprocessors used to work with subexpressions, but the
      # functionality was removed. See #15948.
      a = symbols("a")
      x = SymbolInMulOnce("x")
      w = SymbolRemovesOtherSymbols("w")
      assert 3 * a * w**2 == 3 * w**2
      assert 3 * a * x**3 * w**2 == 3 * w**2
  
      x = SubclassSymbolInMulOnce("x")
      w = SubclassSymbolRemovesOtherSymbols("w")
      assert 3 * a * w**2 == 3 * w**2
      assert 3 * a * x**3 * w**2 == 3 * w**2
  
file_path: sympy/sympy/core/tests/test_constructor_postprocessor.py
imports: from sympy.core.basic import Basic
  from sympy.core.mul import Mul
  from sympy.core.symbol import Symbol, symbols
  from sympy.testing.pytest import XFAIL
label_desc: Use image node_id 4 for calling a global function with example usage: test_subexpression_postprocessors() without return types