ALBERT Modeling + required changes to utilities

src/transformers/file_utils.py

@@ -105,7 +105,25 @@ def is_tf_available():
 
 def add_start_docstrings(*docstr):
     def docstring_decorator(fn):
-        fn.__doc__ = "".join(docstr) + fn.__doc__
+        fn.__doc__ = "".join(docstr) + (fn.__doc__ if fn.__doc__ is not None else "")
+        return fn
+
+    return docstring_decorator
+
+
+def add_start_docstrings_to_callable(*docstr):
+    def docstring_decorator(fn):
+        class_name = ":class:`~transformers.{}`".format(fn.__qualname__.split(".")[0])
+        intro = "   The {} forward method, overrides the :func:`__call__` special method.".format(class_name)
+        note = r""" 
+    
+    .. note::
+        Although the recipe for forward pass needs to be defined within
+        this function, one should call the :class:`Module` instance afterwards
+        instead of this since the former takes care of running the
+        registered hooks while the latter silently ignores them.
+        """
+        fn.__doc__ = intro + note + "".join(docstr) + (fn.__doc__ if fn.__doc__ is not None else "")
         return fn
 
     return docstring_decorator