[tryton] update an existing dataset by clicking a button

[kaheinzelmann0]

Hello, 

i have a tree view which contains a button on each record. 
Now i want to edit/update the values of fields of the row if clicking the 
button. 

But i donk konw how to get the ID of the row and how to update. 
I tried something like this: 

def myButton(cls, records):
     pool = Pool()
     Model = pool.get(mymodul.mymodul)
     row = Model.search(['field1','=','test'])

But as i said, i don't know how to get the ID of the ckicked row and i 
don't found an update command.