text: from rest_framework import serializers
  from todoApp.models import Todo, Group
  from django.contrib.auth.models import User
  
  class UserSerializer(serializers.HyperlinkedModelSerializer):
      class Meta:
          model = User
          fields = '__all__'
  
  class TodoSerializer(serializers.ModelSerializer):
      owner = serializers.ReadOnlyField(source='owner.username')
  
      class Meta:
          model = Todo
          fields = ('owner','id', 'title', 'note', 'completed')
  
  class GroupSerializer(serializers.ModelSerializer):
      class Meta:
          model = Group
          fields = ('name', 'address', 'manager', 'parent_group', 'contact', 'phone', 'email')
  
  class RegistrationSerializer(serializers.ModelSerializer):
      class Meta:
          model = User
          fields = ('username', 'password')