'Create filename suffix: "." + first value of self.PARSER_TAGS["file_ext"],
or None if self.PARSER_TAGS["file_ext"] doesn\'t exist.'

def createFilenameSuffix(self):

    file_ext = self.getParserTags().get('file_ext')
    if isinstance(file_ext, (tuple, list)):
        file_ext = file_ext[0]
    return (file_ext and ('.' + file_ext))
