code: def validate_unique(self, *args, **kwargs):
          
          super(EighthSignup, self).validate_unique(*args, **kwargs)
  
          if self.has_conflict():
              raise ValidationError({NON_FIELD_ERRORS: ("EighthSignup already exists for the User and the EighthScheduledActivity's block",)})
docs: Checked whether more than one EighthSignup exists for a User on a given EighthBlock.