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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 encrypt_file_inline(filename, passphrase):
 """Encrypt file inline, with an optional passphrase. If you set the passphrase to None, a default is used. This will make you vulnerable to confirmation attacks and learn-partial-information attacks. :param filename: The name of the file to encrypt. :type filename: str :param passphrase: The passphrase used to decrypt the file. :type passphrase: str or None :returns: The key required to decrypt the file. :rtype: str """

    key = key_generators.key_from_file(filename, passphrase)

    inline_transform(filename, key)

    return key