Format unhashed feature: show first (most probable) candidate,
    display other candidates in title attribute.

def _format_unhashed_feature(feature, weight, hl_spaces):
    # type: (...) -> str
    """ Format unhashed feature: show first (most probable) candidate,
    display other candidates in title attribute.
    """
    if not feature:
        return ''
    else:
        first, rest = feature[0], feature[1:]
        html = format_signed(
            first, lambda x: _format_single_feature(x, weight, hl_spaces))
        if rest:
            html += ' <span title="{}">&hellip;</span>'.format(
                '\n'.join(html_escape(format_signed(f)) for f in rest))
        return html