  ### PrimaryKey relationships
  
  class PrimaryKeyRelatedField(RelatedField):
      """
      Serializes a related field or related object to a pk value.
      """
  
      def to_native(self, pk):
          return pk
  
 
</s> remove     Serializes a to-many related field or related manager to a pk value.
 </s> add     Represents a to-many relationship as a pk value. </s> remove     A field that represents the model's identity using a hyperlink.
 </s> add     Represents the instance, or a property on the instance, using hyperlinking.
    Represents a to-one relationship as a pk value.
  ### PrimaryKey relationships
  
  class PrimaryKeyRelatedField(RelatedField):
      """
    Represents a to-one relationship as a pk value.
      """
  
      def to_native(self, pk):
          return pk
  
keep keep keep keep replace keep keep keep keep keep
 Relational field support in browseable API.

Add slug relational fields.
Add quickstart. 
rest_framework/fields.py