class UserLoginSerializer(ModelSerializer):
    token = CharField(allow_blank=True, read_only=True)
    username = CharField(required=False, allow_blank=True)
    email = EmailField(label='Email Address',required=False, allow_blank=True)  
    def validate(self, data):
        user_obj = None
        email = data.get('email', None)
        username = data.get('username', None)
        password = data.get('password', None)
        if not email and not username:
            raise ValidationError("A username or email is required to login.")
        user_qs = User.objects.filter(
            Q(email=email) | 
            Q(username=username) ).distinct()
        user_qs = user_qs.exclude(email__isnull=True).exclude(email__iexact="")
        if user_qs.exists() and user_qs.count() == 1:
            user_obj = user_qs.first()
        else:
            raise ValidationError("This username/email is not valid.")
        if user_obj:
            if not user_obj.check_password(password):
                raise ValidationError("Incorrent credentials please try again.")
        data["token"] = "SOME RANDOM TOKEN"
        return data