text: from django.contrib.auth.models import User
  from rest_framework import serializers
  
  
  class UserInfoOut(serializers.ModelSerializer):
      class Meta:
          model = User
          fields = ('id', 'username', 'first_name', 'last_name', 'email')
  
  
  class ChangePwdIn(serializers.Serializer):
      old_password = serializers.CharField(max_length=128)
      new_password = serializers.CharField(max_length=128)
  
      def create(self, validated_data):
          pass
  
      def update(self, instance, validated_data):
          pass
  
  
  class ChangePwdOut(serializers.Serializer):
      success = serializers.BooleanField(default=False)
  
      def create(self, validated_data):
          pass
  
      def update(self, instance, validated_data):
          pass
  
  
  class UpdateUserInfoIn(serializers.Serializer):
      email = serializers.EmailField(required=False)
      first_name = serializers.CharField(max_length=128, required=False)
      last_name = serializers.CharField(max_length=128, required=False)
  
      def create(self, validated_data):
          pass
  
      def update(self, instance, validated_data):
          pass
  