improve type signature of visitor

src/Parser/__init__.py

@@ -94,7 +94,7 @@ class JobShopVisitor(arpeggio.PTNodeVisitor):
             print("problem_data\nchildren:", children)
         # filter out newlines or other strings
         cleaned_data = list(filter(lambda x: type(x) is not str, children))
-        problem_data: List[List] = [ cleaned_data[i] for i in range(2, len(cleaned_data))]
+        problem_data: List[List[Tuple[int, int]]] = [ cleaned_data[i] for i in range(2, len(cleaned_data))]
         problem = JobShopProblem(children[0], children[1], problem_data)
         if self.debug:
             print("\nreturning a", type(problem), "\n")