old_contents: from rest_framework import serializers as ser
  
  from api.base.serializers import JSONAPISerializer, LinksField, JSONAPIListField
  
  class TaxonomyField(ser.Field):
      def to_representation(self, obj):
          if obj is not None:
              return {'id': obj._id,
                      'text': obj.text}
          return None
  
      def to_internal_value(self, data):
          return data
  
  class TaxonomySerializer(JSONAPISerializer):
      filterable_fields = frozenset([
          'text',
          'parents',
          'id'
      ])
      id = ser.CharField(source='_id', required=True)
      text = ser.CharField(max_length=200)
      parents = JSONAPIListField(child=TaxonomyField())
  
      links = LinksField({
          'parents': 'get_parent_urls',
          'self': 'get_absolute_url',
      })
  
      def get_parent_urls(self, obj):
          return [p.get_absolute_url() for p in obj.parents]
  
      def get_absolute_url(self, obj):
          return obj.get_absolute_url()
  
      class Meta:
          type_ = 'taxonomies'
  
new_contents: from rest_framework import serializers as ser
  
  from api.base.serializers import JSONAPISerializer, LinksField, JSONAPIListField
  
  class TaxonomyField(ser.Field):
      def to_representation(self, obj):
          if obj is not None:
              return {'id': obj._id,
                      'text': obj.text}
          return None
  
      def to_internal_value(self, data):
          return data
  
  class TaxonomySerializer(JSONAPISerializer):
      filterable_fields = frozenset([
          'text',
          'parents',
          'id'
      ])
      id = ser.CharField(source='_id', required=True)
      text = ser.CharField(max_length=200)
      parents = JSONAPIListField(child=TaxonomyField())
      child_count = ser.IntegerField()
  
      links = LinksField({
          'parents': 'get_parent_urls',
          'self': 'get_absolute_url',
      })
  
      def get_parent_urls(self, obj):
          return [p.get_absolute_url() for p in obj.parents]
  
      def get_absolute_url(self, obj):
          return obj.get_absolute_url()
  
      class Meta:
          type_ = 'taxonomies'
  
subject: Add child_count taken from new Subject property