问Django Rest框架:禁止将TypeError直接分配到多到多集的前侧。

EN

class User(models.Model):
    username = models.CharField(primary_key=True, max_length=32, unique=True)
    user_email = models.EmailField(max_length=32, unique=False) # Validates an email through predefined regex which checks ‘@’ and a ‘.’
    user_password = models.CharField(max_length=32)
    user_avatar_path = models.CharField(max_length=64)

class Group(models.Model):
    group_id = models.AutoField(primary_key=True)
    group_name = models.CharField(max_length=32, unique=False)
    group_admin = models.ForeignKey(
        User, 
        on_delete=models.CASCADE, 
        related_name='my_groups'
        )
    members = models.ManyToManyField(
        User,
        related_name='groups', # The name to use for the relation from the related object back to this one.
        through='UserGroup' # Attaches a Junction table to the Many to Many relationship.
        )

class UserGroup(models.Model): # Manually specified Junction table for User and Group
    user = models.ForeignKey(
        User, 
        on_delete=models.CASCADE, 
        related_name='user_groups'
        )
    group = models.ForeignKey(
        Group, 
        on_delete=models.CASCADE, 
        related_name='user_groups'
        )

class GroupSerializer(serializers.ModelSerializer):
    members = MemberSerializer(many=True, required=False)
    group_admin = serializers.SlugRelatedField(slug_field='username', queryset=User.objects.all()) # A Group object is related to a User object by username

    class Meta:
        model = Group
        fields = ['group_id', 'group_name', 'group_admin', 'members']

    def create(self, validated_data): # Overriden so that when a group is created, the group admin is automatically declared as a member.
        group = Group.objects.create(**validated_data)
        group_admin_data = validated_data.pop('group_admin')
        group.members.add(group_admin_data)

        return group
    
    def update(self, instance, validated_data):
       members_data = validated_data.pop('members') # Comes from the request body, gets the members list
        #print('output: ' + str(members_data[0].items()))
        add_remove = self.context['add_remove'] # Comes from the View 
        if members_data is not None:
            if add_remove == 'add':
                for member in members_data:
                    instance.members.add(member['username'])
            elif add_remove == 'remove':
                for member in members_data:
                    instance.members.remove(member['username'])  
            
        return super().update(instance, validated_data)

class GroupUpdate(generics.UpdateAPIView):
    serializer_class = GroupSerializer

    def get_object(self):
        queryset = Group.objects.all()
        group_id = self.kwargs['group_id']
        if group_id is not None:
            queryset = queryset.filter(group_id=group_id).first()
        return queryset

    def get_serializer_context(self): # Passes the URL paramters to the GroupSerializer (serializer doesn't have kwargs).
        context = super().get_serializer_context()
        context['add_remove'] = self.kwargs['add_remove']
        print(self.request.data)
        return context

    def perform_update(self, serializer):
        serializer=GroupSerializer(data=self.request.data, partial=True)
        serializer.is_valid(raise_exception=True)
        return super().perform_update(serializer)

{
    "members": [
        {
            "username": "small_man"
        }
    ]
}