[Minor] Bump into a new serialization version. (#425)

Since #419 modifies the serialization method, it is necessary to bump
into a new serialization version.

Signed-off-by: Yuchuan <[email protected]>

Author: Seven-Streams

cpp/support/json_serializer.h

@@ -62,7 +62,7 @@ class SerializeVersion {
    * \brief The current serialization version. When the serialization result of any object in
    * XGrammar is changed, this version should be bumped.
    */
-  static constexpr const char kXGrammarSerializeVersion[] = "v5";
+  static constexpr const char kXGrammarSerializeVersion[] = "v6";
 };
 
 /*!

tests/python/test_serialization.py

@@ -42,7 +42,7 @@ def construct_compiled_grammar():
 
 def test_get_serialization_version():
     """Test the version of the serialized JSON string."""
-    assert xgr.get_serialization_version() == "v5"
+    assert xgr.get_serialization_version() == "v6"
 
 
 def test_serialize_grammar():
@@ -61,7 +61,7 @@ def test_serialize_grammar():
         "complete_fsm": None,
         "per_rule_fsms": [],
         "allow_empty_rule_ids": [],
-        "__VERSION__": "v5",
+        "__VERSION__": "v6",
     }
     # The fsms are the same one, but the start state and end states are different.
     assert json.loads(serialized) == expected_json
@@ -81,14 +81,14 @@ def test_serialize_grammar_exception():
         "allow_empty_rule_ids": [],
         "complete_fsm": None,
         "per_rule_fsms": [],
-        "__VERSION__": "v5",
+        "__VERSION__": "v6",
     }
 
     expected_json["__VERSION__"] = "v1"  # Change version to trigger error
     with pytest.raises(xgr.DeserializeVersionError):
         xgr.Grammar.deserialize_json(json.dumps(expected_json))
 
-    expected_json["__VERSION__"] = "v5"
+    expected_json["__VERSION__"] = "v6"
     expected_json.pop("rules")  # Remove required field to trigger error
     with pytest.raises(xgr.DeserializeFormatError):
         xgr.Grammar.deserialize_json(json.dumps(expected_json))
@@ -140,7 +140,7 @@ def test_serialize_tokenizer_info():
         '"decoded_vocab":["1","212","a","A","b","\\u00e4\\u00b8\\u0080","-","aBc","abc"],'
         '"sorted_decoded_vocab":[[6,"-"],[3,"A"],[2,"a"],[7,"aBc"],[8,"abc"],[4,"b"],[5,"\\u00e4\\u00b8\\u0080"]],'
         '"trie_subtree_nodes_range":[1,2,5,4,5,6,7],'
-        '"__VERSION__":"v5"}'
+        '"__VERSION__":"v6"}'
     )
     assert json.loads(serialized) == json.loads(expected_json)
 
@@ -221,7 +221,7 @@ def test_serialize_compiled_grammar():
             "add_prefix_space": True,
             "stop_token_ids": [0, 1],
         },
-        "__VERSION__": "v5",
+        "__VERSION__": "v6",
     }
 
     class AdaptiveTokenMask(BaseModel):