Fast imports part 3 (#9474)

* New intermediate inits

* Update template

* Avoid importing torch/tf/flax in tokenization unless necessary

* Styling

* Shutup flake8

* Better python version check

src/transformers/models/bert_generation/__init__.py

@@ -16,16 +16,53 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from ...file_utils import is_sentencepiece_available, is_torch_available
-from .configuration_bert_generation import BertGenerationConfig
+from typing import TYPE_CHECKING
 
+from ...file_utils import _BaseLazyModule, is_sentencepiece_available, is_torch_available
+
+
+_import_structure = {
+    "configuration_bert_generation": ["BertGenerationConfig"],
+}
 
 if is_sentencepiece_available():
-    from .tokenization_bert_generation import BertGenerationTokenizer
+    _import_structure["tokenization_bert_generation"] = ["BertGenerationTokenizer"]
 
 if is_torch_available():
-    from .modeling_bert_generation import (
-        BertGenerationDecoder,
-        BertGenerationEncoder,
-        load_tf_weights_in_bert_generation,
-    )
+    _import_structure["modeling_bert_generation"] = [
+        "BertGenerationDecoder",
+        "BertGenerationEncoder",
+        "load_tf_weights_in_bert_generation",
+    ]
+
+
+if TYPE_CHECKING:
+    from .configuration_bert_generation import BertGenerationConfig
+
+    if is_sentencepiece_available():
+        from .tokenization_bert_generation import BertGenerationTokenizer
+
+    if is_torch_available():
+        from .modeling_bert_generation import (
+            BertGenerationDecoder,
+            BertGenerationEncoder,
+            load_tf_weights_in_bert_generation,
+        )
+
+else:
+    import importlib
+    import os
+    import sys
+
+    class _LazyModule(_BaseLazyModule):
+        """
+        Module class that surfaces all objects but only performs associated imports when the objects are requested.
+        """
+
+        __file__ = globals()["__file__"]
+        __path__ = [os.path.dirname(__file__)]
+
+        def _get_module(self, module_name: str):
+            return importlib.import_module("." + module_name, self.__name__)
+
+    sys.modules[__name__] = _LazyModule(__name__, _import_structure)