In this assignment, you will create a Python program that allows users to upload any given file, encrypt it using the cryptography module, decrypt it$,$ and access the decrypted file. Your program should adhere to PEP$8$ formatting guidelines, import the cryptography module, and utilize the correct cryptographic functions for encryption and decryption.

Requirements:

$-$ Adhere to PEP$8$ formatting guidelines.

$-$ Import the cryptography module to utilize cryptographic methods.

$-$ Provide a function to generate a cryptographic key if it doesn't exist. If the key exists, retrieve it and use it for encryption and decryption.

$-$ Implement encryption and decryption functions using the cryptography module.

$-$ Allow users to upload any file type for encryption.

$-$ Decrypt the file back to its original file type and state to be executable like the original

$-$ Your script should be able to encrypt a file and then be exited. When your script is started again, it needs to decrypt the previously encrypted file file using the same key, without raising an $.$InvalidToken error.

Hints:

$-$ The cryptography module is not in the Python standard library and needs to be installed in your virtual environment

$-$ Include conditional statements to determine if a cryptography key exists or should be generated

$-$ Use a $.$env file and env variables to store any necessary keys securely

$-$ Refer to the cryptography documentation for guidance on key generation, encryption, and decryption methods.

$-$ String manipulation may be useful for handling file extensions when encrypting and decrypting files