old_contents: from radar_api.serializers.groups import TinyGroupReferenceField
  from radar_api.serializers.source_types import SourceTypeReferenceField
  
  
  class SourceSerializerMixin(object):
      source_group = TinyGroupReferenceField()
      source_type = SourceTypeReferenceField()
  
      def get_model_exclude(self):
          attrs = super(SourceSerializerMixin, self).get_model_exclude()
          attrs.add('source_group_id')
          return attrs
  
new_contents: from radar_api.serializers.groups import TinyGroupReferenceField
  from radar_api.serializers.source_types import SourceTypeReferenceField
  
  
  class SourceSerializerMixin(object):
      source_group = TinyGroupReferenceField()
      source_type = SourceTypeReferenceField()
  
      def get_model_exclude(self):
          attrs = super(SourceSerializerMixin, self).get_model_exclude()
          attrs.add('source_group_id')
          attrs.add('source_type_id')
          return attrs
  
subject: Exclude source_type_id from serializer