typing: Fix type annotation for identify() return value

Author: Ulthran

beangulp/identify.py

@@ -1,7 +1,7 @@
 __copyright__ = "Copyright (C) 2016  Martin Blais"
 __license__ = "GNU GPLv2"
 
-from typing import List
+from typing import List, Optional
 from beangulp.exceptions import Error
 from beangulp.importer import Importer
 
@@ -12,7 +12,7 @@
 FILE_TOO_LARGE_THRESHOLD = 8 * 1024 * 1024
 
 
-def identify(importers: List[Importer], filepath: str):
+def identify(importers: List[Importer], filepath: str) -> Optional[Importer]:
     """Identify the correct importer to handle a document.
 
     Args: