old_contents: from rest_framework import serializers
  
  from teryt_tree.models import JednostkaAdministracyjna
  from teryt_tree.models import Category
  
  
  class CategorySerializer(serializers.HyperlinkedModelSerializer):
  
      class Meta:
          model = Category
          fields = ('name', 'pk')
  
  
  class JednostkaAdministracyjnaSerializer(serializers.HyperlinkedModelSerializer):
      teryt = serializers.CharField(source='pk', read_only=True)
      url = serializers.CharField(source='get_absolute_url', read_only=True)
      category = CategorySerializer()
      children = serializers.HyperlinkedRelatedField(
          many=True,
          read_only=True,
          view_name='jednostkaadministracyjna-detail'
      )
  
      class Meta:
          model = JednostkaAdministracyjna
          fields = ('url',
                    'parent',
                    'teryt',
                    'children',
                    'category',
                    'name',
                    'updated_on',
                    'active',
                    'level',)
  
new_contents: from rest_framework import serializers
  
  from teryt_tree.models import JednostkaAdministracyjna
  from teryt_tree.models import Category
  
  
  class CategorySerializer(serializers.HyperlinkedModelSerializer):
  
      class Meta:
          model = Category
          fields = ('name', 'pk')
  
  
  class JednostkaAdministracyjnaSerializer(serializers.HyperlinkedModelSerializer):
      teryt = serializers.CharField(source='pk', read_only=True)
      url = serializers.CharField(source='get_absolute_url', read_only=True)
      category = CategorySerializer()
      children = serializers.HyperlinkedRelatedField(
          many=True,
          read_only=True,
          view_name='jednostkaadministracyjna-detail'
      )
  
      class Meta:
          model = JednostkaAdministracyjna
          fields = ('url',
                    'parent',
                    'teryt',
                    'children',
                    'category',
                    'name',
                    'updated_on',
                    'active',
                    'level',)
  
  class SIMCSerializer(serializers.HyperlinkedModelSerializer):
      simc = SIMCSerializer(many=True)
      sym_pod = SIMCSerializer()
      terc = JednostkaAdministracyjnaSerializer()
  
      class Meta:
          model = SIMC
          fields = ['id', 'sym_pod', 'terc', 'name', 'updated_on']
  
subject: Add SIMCSerializer