Cannot override file attribute of EFBMsg

[blueset]

Seems like file of EFBMsg objects cannot be overridden due to the @property attribute of it.

(Not sure if that should be considered as a bug.)

Reproduction code

https://gist.github.com/catbaron0/e91e295b67901fe47aaeabc2e311c305

from typing import Optional
from ehforwarderbot import EFBMiddleware, EFBMsg, coordinator

from tempfile import NamedTemporaryFile

class DebugMiddleware(EFBMiddleware):
    """
    Debug middleware.
    A minimum working example
    """
    middleware_id: str = "debug.DebugMiddleware"
    middleware_name: str = "Debug Middleware"
    __version__: str = '1.0.0'

    @staticmethod
    def sent_by_master(message: EFBMsg) -> bool:
        return message.deliver_to != coordinator.master

    def process_message(self, message: EFBMsg) -> Optional[EFBMsg]:
        """
        Process a message with middleware
        Args:
            message (:obj:`.EFBMsg`): Message object to process
        Returns:
            Optional[:obj:`.EFBMsg`]: Processed message or None if discarded.
        """
        if self.sent_by_master(message) and message.text.startswith('debug`'):
            print("\nStart Debuging...")
            print(f"message.file: {message.file}")

            print("message.file = NamedTemporaryFile()")
            message.file = NamedTemporaryFile()
            print(f"message.file: {message.file}")

            if message.target and message.target.file:
                message.file = message.target.file
                print("message.file = message.target.file")
                print(f"message.target.file: {message.target.file}")
                print(f"message.file: {message.file}")

            print("Debuging Finished\n")
        return message

Ref: Support group Dec. 2019, [2]