title: Django Rest Framework 'RelatedManager' object has no attribute
body: <p>The original error is:</p>
  
  <pre><code>Got AttributeError when attempting to get a value for field `original` on serializer `ProductImageSerializer`.
  The serializer field might be named incorrectly and not match any attribute or key on the `RelatedManager` instance.
  Original exception text was: 'RelatedManager' object has no attribute 'original'.
  </code></pre>
  
  <p>This is my <code>models.py</code>:</p>
  
  <pre><code>class Product(models.Model):
  
      name = models.CharField(max_length=100, db_index=True)
      ean = models.CharField(max_length=13, db_index=True)
  
      ...
  
  class ProductImage(models.Model):
      product = models.ForeignKey(Product, null=True, related_name='images', on_delete=models.CASCADE, db_index=True)
      original = models.ImageField(upload_to=get_uuid_image)
      medium = models.ImageField(upload_to=get_uuid_image)
      small = models.ImageField(upload_to=get_uuid_image)
  </code></pre>
  
  <p>The serializers:</p>
  
  <pre><code>class ProductBasicSerializer(serializers.ModelSerializer):
      tags = TagSerializer(many=True)
      brand = BrandSerializer()
      images = ProductImageSerializer(required=False)
  
      class Meta:
          model = Product
          fields = ['tags', 'brand', "ean", "name", "quantity", "unit", "images"]
  
  
  class ProductImageSerializer(serializers.ModelSerializer):
  
      class Meta:
          model = ProductImage
          exclude = ("product",)
  </code></pre>
  
  <p>And in the view: </p>
  
  <pre><code>product = Product.objects.get(ean=ean)
  serializer = ProductBasicSerializer(product)
  </code></pre>
  
  <p>Why do I get the error <code>RelatedManager' object has no attribute 'original'</code> ? The reverse relationship ProductImage, with <code>related_name="images"</code> does have the attribute <code>original</code>.</p>