'Convert a list to a regex string for matching a directive.
Want possible matching values to be from longest to shortest.  This
prevents the possibility of a match occurring for a value that also
a substring of a larger value that should have matched (e.g., \'abc\'
matching when \'abcdef\' should have been the match).'

def __seqToRE(self, to_convert, directive):

    to_convert = sorted(to_convert, key=len, reverse=True)
    for value in to_convert:
        if (value != ''):
            break
    else:
        return ''
    regex = '|'.join((re_escape(stuff) for stuff in to_convert))
    regex = ('(?P<%s>%s' % (directive, regex))
    return ('%s)' % regex)
