I have this dataframe:

regione	codice_regione	2004_6_1	2004_12_1	2005_6_1	2005_12_1	2006_6_1	2006_12_1
NAME_1		13	9.0	9.0	10.0	10.0	9.0	8.0
Basilicata	17	1.0	1.0	1.0	1.0	1.0	1.0
Calabria	18	3.0	3.0	2.0	2.0	2.0	2.0
Campania	15	8.0	8.0	7.0	6.0	8.0	9.0
Emilia-romagna	8	16.0	16.0	16.0	16.0	16.0	16.0


I want to convert all the columns after codice_regione (except two columns called 'trend1' and 'trend2') into a single column named 'data'