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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(self, k, a, m):
 """ Encrypt accoriding to the selected encryption and hashing functions. :param k: Encryption key (optional) :param a: Additional Authentication Data :param m: Plaintext Returns a dictionary with the computed data. """

        iv = _randombits(96)
        cipher = Cipher(algorithms.AES(k), modes.GCM(iv),
                        backend=self.backend)
        encryptor = cipher.encryptor()
        encryptor.authenticate_additional_data(a)
        e = encryptor.update(m) + encryptor.finalize()

        return (iv, e, encryptor.tag)