code: def _to_DM(A, ans):
      """Convert the answer to DomainMatrix."""
      if isinstance(A, DomainMatrix):
          return A.to_dense()
      elif isinstance(A, DDM):
          return DomainMatrix(list(A), A.shape, A.domain).to_dense()
      elif isinstance(A, SDM):
          return DomainMatrix(dict(A), A.shape, A.domain).to_dense()
      else:
          assert False
  
file_path: sympy/sympy/polys/matrices/tests/test_nullspace.py
imports: from sympy import ZZ, Matrix
  from sympy.polys.matrices import DM, DomainMatrix
  from sympy.polys.matrices.ddm import DDM
  from sympy.polys.matrices.sdm import SDM
  import pytest
label_desc: Use image node_id 1 for calling a global function with example usage: _to_DM(A, ans) and returns: A, DomainMatrix, DomainMatrix