How to copy data to corresponding party

Through a model and form, I enter various data between them, (bank and account number), any idea how this data that you enter through a form can be copied to the corresponding party?.I was trying to do it as follows, it doesn’t work:

    def get_party_cbu(cls, party, bank):        
        pool = Pool()
        data =[
            'bank', '=', bank,
            'owners', '=', party,
        return data       

    def set_party_cbu(cls, name,party):
        pool = Pool()
        bank_ac = pool.get('bank.account')
        bank_ac_number = pool.get('bank.account.number')
          bank_data = {
        bank_data_number = {
            'type': 'iban',
            'number': cbu,
        Bank_ac = bank_ac.create([bank_data])  
        Bank_ac_number = bank_ac_number.create([bank_data_number])

I would suggest you first to follow Python coding style by using CamelCase for classes and lower case for instance (experienced developers have a lot of difficulties to read your code).
Also it will be even more readable to use a singular name for single instance and plural name for a list of instances.

What is the definition of the Function which is using those getter and setter?

A getter function (when it is a class method) receive a list of instances and the name of the Function field for which it computes the value.
It can also be an instance method so there is no list of instances obviously.

A getter can not return instances but only raw value that correspond to the field.

A setter function receive a value to set and a list of record instances on which to set the value.