def METHOD_NAME(self):
    """Get one dictionary whose key is gene symbol and value is
    tissue expression data (list type).  All keys are lower case.
    The output is a symbolValuepairDict (dictionary): one
    dictionary of Symbol and Value Pair; key is symbol, value is
    one list of expression values of one probeSet;
    """
    id_list = [self.data[symbol].data_id for symbol in self.data]
    symbol_values_dict = {}
    if len(id_list) > 0:
        results = []
        with self.conn.cursor() as cursor:
            cursor.execute(
                "SELECT TissueProbeSetXRef.Symbol, TissueProbeSetData.value "
                "FROM TissueProbeSetXRef, TissueProbeSetData"
                f" WHERE TissueProbeSetData.Id IN ({', '.join(['%s'] * len(id_list))})"
                " AND TissueProbeSetXRef.DataId = TissueProbeSetData.Id"
                ,tuple(id_list))
            results = cursor.fetchall()
            for result in results:
                (symbol, value) = result
                if symbol.lower() not in symbol_values_dict:
                    symbol_values_dict[symbol.lower()] = [value]
                else:
                    symbol_values_dict[symbol.lower()].append(
                        value)
    return symbol_values_dict