class UserServiceWizard(SessionWizardView):
    instance = None

def get_form(self, step=None, data=None, files=None):
    if step is None:
        step = self.steps.current
prev_data = self.get_cleaned_data_for_step(self.get_prev_step(self.steps.
    current))
if step == '1':
    service_name = str(prev_data['provider']).split('Service')[1]
form_class = class_for_name('th_' + service_name.lower() + '.forms', 
    service_name + 'ProviderForm')
form = form_class(data)
Django FormWizard, как динамически изменять form_list