def set_trailer(name, value):
    """Sets the given chunk trailing header, ``name`` and ``value``. If 
        there is already a trailing header by ``name`` present, it will be
        overwritten. Returns the new value for header name as byte-string.

        ``name``,
            byte-string of header field name, in lower case.

        ``value``,
            any type, which can be converted to string.
        """
