[gemma4] Fix isort/black lint errors in __init__.py and tokenizer.py

Author: Yunchao Yang

src/fairseq2/models/gemma4/__init__.py

@@ -24,13 +24,13 @@
 )
 from fairseq2.models.gemma4.config import GEMMA4_FAMILY as GEMMA4_FAMILY
 from fairseq2.models.gemma4.config import Gemma4Config as Gemma4Config
+from fairseq2.models.gemma4.config import get_gemma4_12b_config as get_gemma4_12b_config
 from fairseq2.models.gemma4.config import (
     get_gemma4_26b_a4b_config as get_gemma4_26b_a4b_config,
 )
 from fairseq2.models.gemma4.config import get_gemma4_31b_config as get_gemma4_31b_config
 from fairseq2.models.gemma4.config import get_gemma4_e2b_config as get_gemma4_e2b_config
 from fairseq2.models.gemma4.config import get_gemma4_e4b_config as get_gemma4_e4b_config
-from fairseq2.models.gemma4.config import get_gemma4_12b_config as get_gemma4_12b_config
 from fairseq2.models.gemma4.config import (
     register_gemma4_configs as register_gemma4_configs,
 )
@@ -84,6 +84,7 @@
     "apply_fsdp_to_gemma4",
     "convert_gemma4_state_dict",
     "create_gemma4_model",
+    "get_gemma4_12b_config",
     "get_gemma4_26b_a4b_config",
     "get_gemma4_31b_config",
     "get_gemma4_e2b_config",

src/fairseq2/models/gemma4/tokenizer.py

@@ -58,7 +58,10 @@ def create_encoder(
             raise ValueError(f"`lang` must be `None`, but is '{lang}' instead.")
 
         if mode is not None and mode not in (
-            "default", "prompt", "prompt_response", "as_is"
+            "default",
+            "prompt",
+            "prompt_response",
+            "as_is",
         ):
             raise ValueError(
                 "`mode` must be 'default', 'prompt', 'prompt_response', or "