django -Аргумент int должен быть строкой или числом, а не «Кортежом»

Я смотрю на это уже пару часов и никак не могу понять, почему я получаю это сообщение...

int() argument must be a string or a number, not 'tuple'

в этой строке из моего views.py (ПРИМЕЧАНИЕ :Исключение на самом деле возникает на один уровень глубже внутри ядра django, но это моя строка кода, которая в конечном итоге вызывает исключение )...

service_interest = ServiceInterest.objects.get_or_create(service = service, client = client)

Почему я получаю эту ошибку? Для вашего удобства см. ниже models.py, Forms.py и фрагмент из views.py.

models.py:

class Client(models.Model):
  name = models.CharField(max_length=100)
  email = models.EmailField()
  site = models.URLField()
  contact_date = models.DateField(default = datetime.date.today())

class Service(models.Model):
  name = models.CharField(max_length=200)

class ServiceInterest(models.Model):
  service = models.ForeignKey('Service')
  client = models.ForeignKey('Client')

  class Meta:
    unique_together = ("service", "client")

формы.py...

class ContactForm(forms.Form):


SERVICE_CHOICES = (
    ('first_choice', 'Description of first choice'),
    ('second_choice', 'Description of second choice'),
    ('third_choice', 'Description of third choice'),
    ('other', 'Other')
  )

  SERVICE_CHOICES_DICT = dict(SERVICE_CHOICES)

  name = forms.CharField(label='What would you like us to call you?', max_length=200, required=False)
  email = forms.EmailField(label='What is your email address?', help_text='Ex: yourname@gmail.com')
  url = forms.URLField(label='If you have a website, please provide a link', required=False, help_text="Ex: www.yoursite.com")
  service_interest = forms.MultipleChoiceField(label="Please check all of the services you're interested in:", widget=forms.widgets.CheckboxSelectMultiple, choices=SERVICE_CHOICES, required=True)
  other = forms.CharField(label='If you selected \"Other\", please specify:', max_length=200, required=False)
  message = forms.CharField(max_length=10000, required=False, label='Any other information you think we should know?', widget=forms.widgets.Textarea)

  def clean_other(self):
    cleaned_data = super(ContactForm, self).clean()
    if 'service_interest' in cleaned_data.keys():
      options = cleaned_data['service_interest']
      if 'other' in options:
        other_input = cleaned_data['other']
        if other_input == None or len(other_input) == 0:
          raise forms.ValidationError('Required when \"Other\" is checked')

    return cleaned_data

соответствующий код из views.py:

  name = form.cleaned_data['name']
  email = form.cleaned_data['email']
  url = form.cleaned_data['url']
  interests = form.cleaned_data['service_interest']
  other = form.cleaned_data['other']
  message = form.cleaned_data['message']

  client = Client.objects.get_or_create(name = name, email = email, site = url)
  for interest in interests:
    service = None
    if(interest != 'other'):
      service = Service.objects.get_or_create(name = ContactForm.SERVICE_CHOICES_DICT[interest])
    else:
      service = Service.objects.get_or_create(name = other)

    # Appears to be responsible for the stack trace, even though exception
    # is one level deeper in...
    # /Library/Python/2.7/site-packages/django/core/handlers/base.py in get_response
    service_interest = ServiceInterest.objects.get_or_create(service = service, client = client)