django - DRF serializer.save () object is not iterable -

when try save extended data object in modelsetview

def perform_create(self, serializer):         serializer.save(from_user=self.request.user) 

i error: 'user' object not iterable

drf version 3.1.3 doing wrong?

class mailviewset(viewsets.modelviewset):     model = mail     queryset = mail.objects.all()     serializer_class = createmailserializer      def get_serializer_class(self):         if self.request.method == 'post':             return createmailserializer         return mailserializer       def perform_create(self, serializer):         serializer.save(from_user=self.request.user)   class mail(models.model):     name = models.charfield(max_length=200)     text = models.textfield()     from_user = models.foreignkey(user, related_name='from_users')     to_users = models.manytomanyfield(user, blank=true, null=true, related_name='to_users')    class createmailserializer(serializers.modelserializer):     to_users = emailrelationfield(queryset=user.objects.all())      class meta:         model = mail