code: def test_FreeGroupElm__len__():
      assert len(x**5 * y * x**2 * y**-4 * x) == 13
      assert len(x**17) == 17
      assert len(y**0) == 0
  
imports: from sympy.combinatorics.free_groups import free_group, FreeGroup
  from sympy.core import Symbol
  from sympy.testing.pytest import raises
  from sympy.core.numbers import oo
label_desc: Use image node_id 16 for calling a global function with example usage: test_FreeGroupElm__len__() without return types