code: def test_projection_mat(D):
      p1 = null_space_projection_mat(A=constraint_mat(S), D=D)
      p2 = projection_mat(S=S, D=D)
      assert (np.abs(p1 - p2)).sum() < TOL
  
imports: from typing import Optional
  import numpy
  import pytest
  from gluonts.mx.model.deepvar_hierarchical._estimator import projection_mat
label_desc: Use image node_id 3 for calling a global function with example usage: test_projection_mat(D) without return types