in my model.py, I have:

totFee = fields.Float(compute='_compute_totFee')

@api.depends('field1','field2')
def _compute_totFee(self):  
    for rec in self:  
        self.totFee = 44

I get an error message:

 ERROR crc openerp.http: Exception during JSON request handling.
Traceback (most recent call last):
  File "/opt/odoo/openerp/http.py", line 643, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/opt/odoo/openerp/http.py", line 680, in dispatch
    result = self._call_function(**self.params)
  File "/opt/odoo/openerp/http.py", line 316, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/opt/odoo/openerp/service/model.py", line 118, in wrapper
    return f(dbname, *args, **kwargs)
  File "/opt/odoo/openerp/http.py", line 309, in checked_call
    result = self.endpoint(*a, **kw)
  File "/opt/odoo/openerp/http.py", line 959, in __call__
    return self.method(*args, **kw)
  File "/opt/odoo/openerp/http.py", line 509, in response_wrap
    response = f(*args, **kw)
  File "/opt/enterprise-9/web/controllers/main.py", line 911, in call_kw
    return self._call_kw(model, method, args, kwargs)
  File "/opt/enterprise-9/web/controllers/main.py", line 903, in _call_kw
    return getattr(request.registry.get(model), method)(request.cr, request.uid, *args, **kwargs)
  File "/opt/odoo/openerp/api.py", line 250, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/openerp/models.py", line 3193, in read
    result = BaseModel.read(records, fields, load=load)
  File "/opt/odoo/openerp/api.py", line 248, in wrapper
    return new_api(self, *args, **kwargs)
  File "/opt/odoo/openerp/models.py", line 3239, in read
    values[name] = field.convert_to_read(record[name], use_name_get)
  File "/opt/odoo/openerp/models.py", line 5740, in __getitem__
    return self._fields[key].__get__(self, type(self))
  File "/opt/odoo/openerp/fields.py", line 829, in __get__
    self.determine_value(record)
  File "/opt/odoo/openerp/fields.py", line 936, in determine_value
    self.compute_value(recs)
  File "/opt/odoo/openerp/fields.py", line 891, in compute_value
    self._compute_value(records)
  File "/opt/odoo/openerp/fields.py", line 881, in _compute_value
    getattr(records, self.compute)()
AttributeError: 'transactions' object has no attribute '_compute_totFee'

how would I write that function?

TIA