      def __str__(self):
          return self.name
  
  
  @python_2_unicode_compatible
  class Car(models.Model):
      name = models.CharField(max_length=20)
      default_parts = models.ManyToManyField(Part)
      optional_parts = models.ManyToManyField(Part, related_name='cars_optional')
  
 
</s> remove @python_2_unicode_compatible
 </s> add  </s> remove @python_2_unicode_compatible
 </s> add  </s> remove @python_2_unicode_compatible
 </s> add  </s> remove @python_2_unicode_compatible
 </s> add  </s> remove @python_2_unicode_compatible
 </s> add 
      def __str__(self):
          return self.name
  
  

  class Car(models.Model):
      name = models.CharField(max_length=20)
      default_parts = models.ManyToManyField(Part)
      optional_parts = models.ManyToManyField(Part, related_name='cars_optional')
  
keep keep keep keep replace keep keep keep keep keep
 Refs #23919 -- Removed python_2_unicode_compatible decorator usage 
tests/m2m_signals/models.py