Tastypie Related fields example

## models.py
class UserProfile(models.Model):
    username = models.CharField(max_length=100, blank=True, null=True)
    email = models.EmailField()
    friends = models.ManyToManyField('self')

## resources.py
class UserProfileResource(ModelResource):
    friends = fields.ToManyField('self', 'friends')

    class Meta:
        queryset = UserProfile.objects.all()
        filtering = {
            'friends': ['exact'],
        }

## Queries:
  - friends=1           ## Works
  - friends__friends=1  ## Fails unless I use ALL_WITH_RELATIONS in filtering

## Tastypie lines concerned:
## https://github.com/toastdriven/django-tastypie/blob/master/tastypie/resources.py#L1625-1626