code: def test_combine_powers():
      assert (C**1) ** 1 == C
      assert (C**2) ** 3 == MatPow(C, 6)
      assert (C**-2) ** -3 == MatPow(C, 6)
      assert (C**-1) ** -1 == C
      assert (((C**2) ** 3) ** 4) ** 5 == MatPow(C, 120)
      assert (C**n) ** n == C ** (n**2)
  
imports: from sympy.functions.elementary.miscellaneous import sqrt
  from sympy.simplify.powsimp import powsimp
  from sympy.testing.pytest import raises
  from sympy.core.expr import unchanged
  from sympy.core import symbols, S
  from sympy.matrices import Identity, MatrixSymbol, ImmutableMatrix, ZeroMatrix, OneMatrix, Matrix
  from sympy.matrices.exceptions import NonSquareMatrixError
  from sympy.matrices.expressions import MatPow, MatAdd, MatMul
  from sympy.matrices.expressions.inverse import Inverse
  from sympy.matrices.expressions.matexpr import MatrixElement
label_desc: Use image node_id 15 for calling a global function with example usage: test_combine_powers() without return types