Implement LastNDayOfMonthExpression

src/apscheduler/triggers/cron/expressions.py

@@ -256,15 +256,15 @@ def __str__(self) -> str:
 class LastNDayOfMonthExpression(AllExpression):
     value_re = re.compile(r"last-(?P<last_day>[0-9]+)", re.IGNORECASE)
 
-    def __init__(self, last_day):
+    def __init__(self, last_day: str):
         super().__init__(None)
         self.last_day = as_int(last_day)
 
-    def get_next_value(self, date, field):
-        currval = field.get_value(date)
-        nextval = monthrange(date.year, date.month)[1] - self.last_day
+    def get_next_value(self, dateval: datetime, field: BaseField) -> int | None:
+        currval = field.get_value(dateval)
+        nextval = monthrange(dateval.year, dateval.month)[1] - self.last_day
 
         return nextval if currval <= nextval else None
 
-    def __str__(self):
+    def __str__(self) -> str:
         return f"last-{self.last_day}"