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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, plaintext, encoder=encoding.RawEncoder):
 """ Encrypts the plaintext message using a random-generated ephemeral keypair and returns a "composed ciphertext", containing both the public part of the keypair and the ciphertext proper, encoded with the encoder. The private part of the ephemeral key-pair will be scrubbed before returning the ciphertext, therefore, the sender will not be able to decrypt the generated ciphertext. :param plaintext: [:class:`bytes`] The plaintext message to encrypt :param encoder: The encoder to use to encode the ciphertext :return bytes: encoded ciphertext """


        ciphertext = nacl.bindings.crypto_box_seal(
            plaintext,
            self._public_key
        )

        encoded_ciphertext = encoder.encode(ciphertext)

        return encoded_ciphertext