code: def test_bug_13636():
      """Test issue 13636 regarding handling traces of sums of products
      of GammaMatrix mixed with other factors."""
      pi, ki, pf = tensor_heads("pi, ki, pf", [LorentzIndex])
      i0, i1, i2, i3, i4 = tensor_indices("i0:5", LorentzIndex)
      x = Symbol("x")
      pis = pi(i2) * G(-i2)
      kis = ki(i3) * G(-i3)
      pfs = pf(i4) * G(-i4)
  
      a = pfs * G(i0) * kis * G(i1) * pis * G(-i1) * kis * G(-i0)
      b = pfs * G(i0) * kis * G(i1) * pis * x * G(-i0) * pi(-i1)
      ta = gamma_trace(a)
      tb = gamma_trace(b)
      t_a_plus_b = gamma_trace(a + b)
      assert ta == 4 * (
          -4 * ki(i0) * ki(-i0) * pf(i1) * pi(-i1)
          + 8 * ki(i0) * ki(i1) * pf(-i0) * pi(-i1)
      )
      assert tb == -8 * x * ki(i0) * pf(-i0) * pi(i1) * pi(-i1)
      assert t_a_plus_b == ta + tb
  
file_path: sympy/sympy/physics/hep/tests/test_gamma_matrices.py
imports: from sympy.matrices.dense import eye, Matrix
  from sympy.tensor.tensor import tensor_indices, TensorHead, tensor_heads, TensExpr, canon_bp
  from sympy.physics.hep.gamma_matrices import GammaMatrix, LorentzIndex, kahane_simplify, gamma_trace, _simplify_single_line, simplify_gamma_expression
  from sympy import Symbol
label_desc: Use image node_id 7 for calling a global function with example usage: test_bug_13636() without return types