Fix get_sparse_operator to handle unsimplified QubitOperator

Author: Aniketsy

src/openfermion/linalg/sparse_tools_test.py

@@ -1829,6 +1829,11 @@ def test_sparse_matrix_linearity(self):
         self.assertEqual(list(sparse2.data), [2] * 8)
         self.assertEqual(list(sparse2.indices), [0, 3, 5, 6, 9, 10, 12, 15])
 
+    def test_get_sparse_operator_simplifies_qubit_operator(self):
+        op = QubitOperator('X0') + QubitOperator('X0')
+        sparse = get_sparse_operator(op)
+        self.assertIsNotNone(sparse)
+
 
 class GetSparseOperatorFermionTest(unittest.TestCase):
     def test_sparse_matrix_zero_n_qubit(self):