Support converting models with multiple chat templates

Adds the following metadata:
* tokenizer.chat_templates
* tokenizer.chat_template.<name1>
* tokenizer.chat_template.<name2>
* tokenizer.chat_template.<...>

Where `tokenizer.chat_templates` is an array of the template names (except `default`), `default` is added to the regular `tokenizer.chat_template`.

Author: CISC

gguf-py/gguf/constants.py

@@ -90,6 +90,8 @@ class Tokenizer:
         HF_JSON          = "tokenizer.huggingface.json"
         RWKV             = "tokenizer.rwkv.world"
         CHAT_TEMPLATE    = "tokenizer.chat_template"
+        CHAT_TEMPLATE_N  = "tokenizer.chat_template.{name}"
+        CHAT_TEMPLATES   = "tokenizer.chat_templates"
 
 
 #

gguf-py/gguf/gguf_writer.py

@@ -6,7 +6,8 @@
 import tempfile
 from enum import Enum, auto
 from io import BufferedWriter
-from typing import IO, Any, Sequence
+from typing import IO, Any, Sequence, Mapping
+from string import ascii_letters, digits
 
 import numpy as np
 
@@ -466,7 +467,33 @@ def add_add_eos_token(self, value: bool) -> None:
     def add_add_space_prefix(self, value: bool) -> None:
         self.add_bool(Keys.Tokenizer.ADD_PREFIX, value)
 
-    def add_chat_template(self, value: str) -> None:
+    def add_chat_template(self, value: str | Sequence[Mapping[str, str]]) -> None:
+        if isinstance(value, list):
+            template_default = None
+            template_names = set()
+
+            for choice in value:
+                name = choice.get('name', '')
+                template = choice.get('template')
+
+                # Allowing non-alphanumerical characters in template name is probably not a good idea, so filter it
+                name = ''.join((c for c in name if c in ['_'] + list(ascii_letters) + list(digits)))
+
+                if name and template is not None:
+                    if name == 'default':
+                        template_default = template
+                    else:
+                        template_names.add(name)
+                        self.add_string(Keys.Tokenizer.CHAT_TEMPLATE_N.format(name=name), template)
+
+            if template_names:
+                self.add_array(Keys.Tokenizer.CHAT_TEMPLATES, list(template_names))
+
+            if template_default is None:
+                return
+
+            value = template_default
+
         self.add_string(Keys.Tokenizer.CHAT_TEMPLATE, value)
 
     def _pack(self, fmt: str, value: Any, skip_pack_prefix: bool = False) -> bytes:

gguf-py/gguf/vocab.py

@@ -141,7 +141,7 @@ def _try_load_from_tokenizer_json(self, path: Path) -> bool:
         with open(tokenizer_config_file, encoding = 'utf-8') as f:
             tokenizer_config = json.load(f)
         chat_template = tokenizer_config.get('chat_template')
-        if chat_template is None or isinstance(chat_template, str):
+        if chat_template is None or isinstance(chat_template, (str, list)):
             self.chat_template = chat_template
         else:
             print(