from enum import IntEnum
from typing import Optional

class Priority(IntEnum):
    LOW = 0
    MIDDLE = 1
    HIGH = 2

values = [
    Priority.LOW,
    Priority.MIDDLE,
    Priority.HIGH]

def format(priority: Priority) -> str:
    if priority == Priority.LOW:
        return "Low"
    elif priority == Priority.MIDDLE:
        return "Middle"
    elif priority == Priority.HIGH:
        return "High"

def parse(string: str) -> Optional[Priority]:
    if string == "Low":
        return Priority.LOW
    elif string == "Middle":
        return Priority.MIDDLE
    elif string == "High":
        return Priority.HIGH
    else:
        return None