def __create_chron_cols(metadata):
        """
        Use to collected chron metadata to create the chron columns
        :param dict metadata: key: variable, val: unit (optional)
        :return list: list of one dict per column
        """
        chron_col_list = []
        chron_col_ct = 1
        for variableName, unit in metadata.items():
            temp_dict = OrderedDict()
            temp_dict['column'] = chron_col_ct
            temp_dict['variableName'] = variableName
            temp_dict['unit'] = unit
            chron_col_list.append(copy.deepcopy(temp_dict))
            chron_col_ct += 1

        return chron_col_list