ments can be used to set
        additional parameters for the header field, with underscores converted
        to dashes.  Normally the parameter will be added as key="value" unless
        value is None, in which case only the key will be added.

        Example:

        h.add_header('content-disposition', 'attachment', filename='bud.gif')

        Note that unlike the corresponding 'email.message' method, this does
        *not* handle '(charset, language, value)' tuples: all values must be
        strings or None.
        N