[MarianTokenizer] implement save_vocabulary and other common methods (#4389)

tests/test_modeling_marian.py

@@ -129,11 +129,6 @@ class TestMarian_EN_DE_More(MarianIntegrationTest):
         max_indices = logits.argmax(-1)
         self.tokenizer.batch_decode(max_indices)
 
-    def test_tokenizer_equivalence(self):
-        batch = self.tokenizer.prepare_translation_batch(["I am a small frog"]).to(torch_device)
-        expected = [38, 121, 14, 697, 38848, 0]
-        self.assertListEqual(expected, batch.input_ids[0].tolist())
-
     def test_unk_support(self):
         t = self.tokenizer
         ids = t.prepare_translation_batch(["||"]).to(torch_device).input_ids[0].tolist()