code: def test_XXM_to_list_flat(DM):
      lol = [[1, 2, 4], [4, 5, 6]]
      assert DM(lol).to_list_flat() == [
          ZZ(1),
          ZZ(2),
          ZZ(4),
          ZZ(4),
          ZZ(5),
          ZZ(6),
      ]
  
imports: from sympy.external.gmpy import GROUND_TYPES
  from sympy import ZZ, QQ, GF, ZZ_I, symbols
  from sympy.polys.matrices.exceptions import DMBadInputError, DMDomainError, DMNonSquareMatrixError, DMNonInvertibleMatrixError, DMShapeError
  from sympy.polys.matrices.domainmatrix import DM, DomainMatrix, DDM, SDM, DFM
  from sympy.testing.pytest import raises, skip
  import pytest
label_desc: Use image node_id 24 for calling a global function with example usage: test_XXM_to_list_flat(DM) without return types