fyDepth: Set by L{set_verify_depth}.

    @ivar _mode: Set by L{set_mode}.

    @ivar _sessionID: Set by L{set_session_id}.

    @ivar _extraCertChain: Accumulated L{list} of all extra certificates added
        by L{add_extra_chain_cert}.

    @ivar _cipherList: Set by L{set_cipher_list}.

    @ivar _dhFilename: Set by L{load_tmp_dh}.

    @ivar _defaultVerifyPathsSet: Set by L{set_default_verify_paths}

    @ivar _ecCurve: Set by L{set_tmp_ecdh}
    r