mutations.py

import mutations

class UserSignup(mutations.Mutation):
    name = mutations.fields.CharField()
    email = mutations.fields.CharField()

    def execute(self):
        user = User.objects.create([...])
        if user.is_referred_through_partner:
            [...]
        else:		  
            self.send_welcome_notification()

    def send_welcome_notification(self):
        if user.is_twitter_signup:
            self.send_message(through='twitter')
        else:
            self.send_message(through='email')