Add inverse chat template metadata support

gguf-py/gguf/constants.py

@@ -166,6 +166,7 @@ class Tokenizer:
         CHAT_TEMPLATE        = "tokenizer.chat_template"
         CHAT_TEMPLATE_N      = "tokenizer.chat_template.{name}"
         CHAT_TEMPLATES       = "tokenizer.chat_templates"
+        INVERSE_TEMPLATE     = "tokenizer.inverse_template"
         # FIM/Infill special tokens constants
         PREFIX_ID            = "tokenizer.ggml.prefix_token_id"
         SUFFIX_ID            = "tokenizer.ggml.suffix_token_id"

gguf-py/gguf/gguf_writer.py

@@ -840,6 +840,9 @@ def add_chat_template(self, value: str | Sequence[Mapping[str, str]]) -> None:
 
         self.add_string(Keys.Tokenizer.CHAT_TEMPLATE, value)
 
+    def add_inverse_template(self, value: str) -> None:
+        self.add_string(Keys.Tokenizer.INVERSE_TEMPLATE, value)
+
     def add_prefix_token_id(self, id: int) -> None:
         self.add_uint32(Keys.Tokenizer.PREFIX_ID, id)
 

gguf-py/gguf/vocab.py

@@ -21,6 +21,7 @@ class SpecialVocab:
     add_special_token: dict[str, bool]
     special_token_ids: dict[str, int]
     chat_template: str | Sequence[Mapping[str, str]] | None
+    inverse_template: str | None
 
     def __init__(
         self, path: str | os.PathLike[str], load_merges: bool = False,
@@ -33,6 +34,7 @@ def __init__(
         self.load_merges = load_merges
         self.merges = []
         self.chat_template = None
+        self.inverse_template = None
         if special_token_types is not None:
             self.special_token_types = special_token_types
         else:
@@ -71,6 +73,10 @@ def add_to_gguf(self, gw: GGUFWriter, quiet: bool = False) -> None:
             if not quiet:
                 logger.info(f'Setting chat_template to {self.chat_template}')
             gw.add_chat_template(self.chat_template)
+        if self.inverse_template is not None:
+            if not quiet:
+                logger.info(f'Setting inverse_template to {self.inverse_template}')
+            gw.add_inverse_template(self.inverse_template)
 
     def _load(self, path: Path) -> None:
         self._try_load_from_tokenizer_json(path)
@@ -137,6 +143,11 @@ def _try_load_from_tokenizer_json(self, path: Path) -> bool:
             self.chat_template = chat_template
         else:
             logger.warning(f'Bad type for chat_template field in {tokenizer_config_file!r} - ignoring')
+        inverse_template = tokenizer_config.get('inverse_template')
+        if inverse_template is None or isinstance(inverse_template, str):
+            self.inverse_template = inverse_template
+        else:
+            logger.warning(f'Bad type for inverse_template field in {tokenizer_config_file!r} - ignoring')
         for typ in self.special_token_types:
             add_entry = tokenizer_config.get(f'add_{typ}_token')
             if isinstance(add_entry, bool):