'Return the appropriate response for the state of the transaction.'

def __call__(self, request):

    self.request = request
    if (request.method == 'GET'):
        if self.should_redirect_to_express():
            return self.redirect_to_express()
        elif self.should_render_confirm_form():
            return self.render_confirm_form()
        elif self.should_render_payment_form():
            return self.render_payment_form()
    elif self.should_validate_confirm_form():
        return self.validate_confirm_form()
    elif self.should_validate_payment_form():
        return self.validate_payment_form()
    return self.render_payment_form()
