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main.py

from __future__ import annotations
from enum import Enum
from typing import Type

menu_msg : str = \
"""
Please select a valid size (1-3): 
1. Small
2. Medium
3. Large
"""

class Size(Enum):
    Small = 1
    Medium = 2
    Large = 3

    @classmethod    
    def prompt_size(cls : Type[Size], prmpt : str) -> Size:
        while True:
            try:
                size: Size = Size(int(input(prmpt)))
                return size
            except ValueError as ex:
                print(ex)
                
print(Size.prompt_size(menu_msg))