def getKnownLanguages(self):
        """Returns all known language locales

        Returns
        -------
        list of strings
            List of language locales used for surveys

        Raises
        ------
        ValueError
            Languages were not able to be found
        """
        sql = """SELECT column_name FROM information_schema.columns
                 WHERE table_name = 'survey_response'"""

        with TRN:
            TRN.add(sql)
            languages = TRN.execute_fetchindex()

        if not languages:
            raise ValueError('Languages were not able to be found')

        languages = [x[0] for x in languages]
        languages_set = set([])
        for i in languages:
            languages_set.add(i)
        return languages_set