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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def decrypt_file(file, key):
 """ Decrypts the file ``file``. The encrypted file is assumed to end with the ``.enc`` extension. The decrypted file is saved to the same location without the ``.enc`` extension. The permissions on the decrypted file are automatically set to 0o600. See also :func:`doctr.local.encrypt_file`. """

    if not file.endswith('.enc'):
        raise ValueError("%s does not end with .enc" % file)

    fer = Fernet(key)

    with open(file, 'rb') as f:
        decrypted_file = fer.decrypt(f.read())

    with open(file[:-4], 'wb') as f:
        f.write(decrypted_file)

    os.chmod(file[:-4], 0o600)