code: def test_XXM_is_lower(DM):
      assert DM([[1, 0, 0], [4, 5, 0]]).is_lower() is True
      assert DM([[1, 2, 3], [4, 5, 6]]).is_lower() is False
  
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 48 for calling a global function with example usage: test_XXM_is_lower(DM) without return types