:param list_: list of dict
        :return: list of string of every key in all the dictionaries

def _get_normalized_columns(cls, list_):
        """
        :param list_: list of dict
        :return: list of string of every key in all the dictionaries
        """
        ret = []
        for row in list_:
            if len(row.keys()) > len(ret):
                ret = cls._ordered_keys(row)

        for row in list_:
            for key in row.keys():
                if key not in ret:
                    ret.append(key)
                    if not isinstance(row, OrderedDict):
                        ret.sort()
        return ret