rameter, using a callback
        registered at the context, or out-of-band via pinentry.

        Keyword arguments:
        recipients	-- list of keys to encrypt to
        sign		-- sign plaintext (default True)
        sink		-- write result to sink instead of returning it
        passphrase	-- for symmetric encryption
        always_trust	-- always trust the keys (default False)
        add_encrypt_to	-- encrypt to configured additional keys (default False)
        prepare		-- (ui) prepare for encryption (default False)
        expect_sign	-- (ui) prepare for signing (default False)
        compress	-- compress plaintext (default True)

        Returns:
        ciphertext	-- the encrypted data (or None if sink is given)
        result		-- additional information about the encryption
        sign_result	-- additional information about the signature(s)

        Raises:
        InvalidRecipients -- if encryption using a particular key failed
        InvalidSigners	-- if signing using a particular key failed
        GPGMEError	-- as signaled by the underlying library

        r