code: def test_DDM_nullspace():
      # more tests are in test_nullspace.py
      A = DDM([[QQ(1), QQ(1)], [QQ(1), QQ(1)]], (2, 2), QQ)
      Anull = DDM([[QQ(-1), QQ(1)]], (1, 2), QQ)
      nonpivots = [1]
      assert A.nullspace() == (Anull, nonpivots)
  
imports: from sympy.testing.pytest import raises
  from sympy.external.gmpy import GROUND_TYPES
  from sympy.polys import ZZ, QQ
  from sympy.polys.matrices.ddm import DDM
  from sympy.polys.matrices.exceptions import DMShapeError, DMNonInvertibleMatrixError, DMDomainError, DMBadInputError
label_desc: Use image node_id 20 for calling a global function with example usage: test_DDM_nullspace() without return types