download_file is fully annotated (Azure#38284)

Author: weirongw23-msft

sdk/storage/azure-storage-file-share/azure/storage/fileshare/_file_client.py

@@ -790,11 +790,10 @@ def abort_copy(self, copy_id: Union[str, FileProperties], **kwargs: Any) -> None
 
     @distributed_trace
     def download_file(
-        self, offset=None,  # type: Optional[int]
-        length=None,  # type: Optional[int]
-        **kwargs  # type: Any
-    ):
-        # type: (...) -> StorageStreamDownloader
+        self, offset: Optional[int] = None,
+        length: Optional[int] = None,
+        **kwargs: Any
+    ) -> StorageStreamDownloader:
         """Downloads a file to the StorageStreamDownloader. The readall() method must
         be used to read all the content or readinto() must be used to download the file into
         a stream. Using chunks() returns an iterator which allows the user to iterate over the content in chunks.