[model] add gemma3n (#8509)

src/llamafactory/data/template.py

@@ -984,6 +984,22 @@ register_template(
 )
 
 
+register_template(
+    name="gemma3n",
+    format_user=StringFormatter(slots=["<start_of_turn>user\n{{content}}<end_of_turn>\n<start_of_turn>model\n"]),
+    format_assistant=StringFormatter(slots=["{{content}}<end_of_turn>\n"]),
+    format_system=StringFormatter(slots=["{{content}}\n\n"]),
+    format_observation=StringFormatter(
+        slots=["<start_of_turn>tool\n{{content}}<end_of_turn>\n<start_of_turn>model\n"]
+    ),
+    format_prefix=EmptyFormatter(slots=[{"bos_token"}]),
+    stop_words=["<end_of_turn>"],
+    replace_eos=True,
+    mm_plugin=get_mm_plugin("gemma3n", image_token="<image_soft_token>", audio_token="<audio_soft_token>"),
+    template_class=Llama2Template,
+)
+
+
 register_template(
     name="glm4",
     format_user=StringFormatter(slots=["<|user|>\n{{content}}<|assistant|>"]),