Add type hints

mythril/laser/smt/bool.py

@@ -86,7 +86,7 @@ class Bool(Expression[z3.BoolRef]):
 
 def And(*args: Union[Bool, bool]) -> Bool:
     """Create an And expression."""
-    union = []
+    union = []    # type: List
     args_list = [arg if isinstance(arg, Bool) else Bool(arg) for arg in args]
     for arg in args_list:
         union += arg.annotations
@@ -108,7 +108,7 @@ def Or(*args: Union[Bool, bool]) -> Bool:
     :return:
     """
     args_list = [arg if isinstance(arg, Bool) else Bool(arg) for arg in args]
-    union = []
+    union = []  # type: List
     for arg in args_list:
         union += arg.annotations
     return Bool(z3.Or([a.raw for a in args_list]), annotations=union)