text: from diofant import FunctionMatrix, Lambda, Matrix, MatrixExpr
  from diofant.abc import i, j
  
  
  __all__ = ()
  
  
  def test_funcmatrix():
      X = FunctionMatrix(3, 3, Lambda((i, j), i - j))
      assert X[1, 1] == 0
      assert X[1, 2] == -1
      assert X.shape == (3, 3)
      assert X.rows == X.cols == 3
      assert Matrix(X) == Matrix(3, 3, lambda i, j: i - j)
      assert isinstance(X*X + X, MatrixExpr)
  