Remove Optional from include parameter

Author: roberthdevries

pandas/io/pytables.py

@@ -580,7 +580,7 @@ def __enter__(self):
     def __exit__(self, exc_type, exc_value, traceback):
         self.close()
 
-    def keys(self, include: Optional[str] = "pandas") -> List[str]:
+    def keys(self, include: str = "pandas") -> List[str]:
         """
         Return a list of keys corresponding to objects stored in HDFStore.