from PR feedback: improve type info

Author: BillTompkins

cmd2/argtypes.py

@@ -91,7 +91,7 @@ def __repr__(self) -> str:
         """Will be printed as the 'argument type' to user on syntax or range error."""
         return f"IntSet{self.range_str}"
 
-    def __call__(self, arg: str) -> Iterable:
+    def __call__(self, arg: str) -> Iterable[int]:
         """Parse a string into an iterable returning ints."""
         if arg == 'all':
             return range(self.bottom, self.top)