code: def test_FreeGroupElm_inverse():
      assert x.inverse() == x**-1
      assert (x * y).inverse() == y**-1 * x**-1
      assert (y * x * y**-1).inverse() == y * x**-1 * y**-1
      assert (y**2 * x**-1).inverse() == x * y**-2
  
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 8 for calling a global function with example usage: test_FreeGroupElm_inverse() without return types