I'm trying to create a function many2one field this field is evaluated based on procession some other fields but I can't access vals dictionary inside the function to be evaluated.

'function' : fields.function(
            _get_cur_function_id,
            type='many2one',
            obj="res.partner.function",
            method=True,
            string='Contract Function'),

def _get_cur_function_id:
     # I want to access vals here, is it possible ?

Note: I'm trying to access this model from XML-RPC and I'm doing this to map a field that's not mandatory to the correct mandatory field (the function field).