code: def test_matrix_symbol_MM():
      X = MatrixSymbol("X", 3, 3)
      Y = eye(3) + X
      assert Y[1, 1] == 1 + X[1, 1]
  
file_path: sympy/sympy/matrices/tests/test_interactions.py
imports: from sympy.core.symbol import symbols
  from sympy.matrices import Matrix, MatrixSymbol, eye, Identity, ImmutableMatrix
  from sympy.matrices.expressions import MatrixExpr, MatAdd
  from sympy.matrices.matrixbase import classof
  from sympy.testing.pytest import raises
label_desc: Use image node_id 4 for calling a global function with example usage: test_matrix_symbol_MM() without return types