running flow through code Django-Viewflow

I want to run my process entirely by code. I've managed to start a process but a I can't run the next part of the process. I tried using the "flow.Function" and calling my desired function but i't says

'Function {} should be called with task instance', 'execute'" 

and the documentation on this subject is'nt very clear.

def create_flow(activation, campos_proceso, **kwargs):
    activation.process.asignador = campos_proceso['asignador']
    activation.process.ejecutor = campos_proceso['ejecutor']
    activation.process.tipo_de_flujo = campos_proceso['tipo_de_flujo']
    activation.process.estado_del_entregable = campos_proceso[
    return activation

def exec_flow(activation, process_fields, **kwargs):
    activation.process.revisor = process_fields['revisor']
    return activation

class Delivery_flow(Flow):
    process_class = DeliveryProcess
    start = flow.StartFunction(create_flow).Next(this.execute)
    execute = flow.Function(exec_flow).Next(this.end)
    end = flow.End()

def Execute(request): #campos_ejecucion, request):
    campos_ejecucion = {
    'observaciones_ejecutor':'Este es un puente magico',
    campos_proceso = {
    return render(request, "Flujo/landing.html")