          models.URLField: URLField,
      })
      _related_class = PrimaryKeyRelatedField
  
      def __init__(self, *args, **kwargs):
          super(ModelSerializer, self).__init__(*args, **kwargs)
          if 'validators' not in kwargs:
              validators = self.get_default_validators()
              if validators:
                  self.validators.extend(validators)
                  self._kwargs['validators'] = validators
  
      def create(self, validated_attrs):
          # Check that the user isn't trying to handle a writable nested field.
          # If we don't do this explicitly they'd likely get a confusing
          # error at the point of calling `Model.objects.create()`.
          assert not any(
 
</s> remove     def __init__(self, *args, **kwargs):
        super(Serializer, self).__init__(*args, **kwargs)

 </s> add     @property
    def fields(self):
        if not hasattr(self, '_fields'):
            self._fields = BindingDict(self)
            for key, value in self.get_fields().items():
                self._fields[key] = value
        return self._fields

    def get_fields(self): </s> remove         self.fields = BindingDict(self)
        for key, value in self._get_base_fields().items():
            self.fields[key] = value

        self.validators = getattr(getattr(self, 'Meta', None), 'validators', [])

    def _get_base_fields(self):
 </s> add  </s> remove         validators = []
 </s> add         validators = getattr(getattr(self, 'Meta', None), 'validators', []) </s> remove                  error_messages=None, validators=[], allow_null=False):
 </s> add                  error_messages=None, validators=None, allow_null=False):
          models.URLField: URLField,
      })
      _related_class = PrimaryKeyRelatedField
  








      def create(self, validated_attrs):
          # Check that the user isn't trying to handle a writable nested field.
          # If we don't do this explicitly they'd likely get a confusing
          # error at the point of calling `Model.objects.create()`.
          assert not any(
keep keep keep keep replace replace replace replace replace replace replace replace keep keep keep keep keep
 Lazy loading of fields and validators. Closes #1963. 
rest_framework/serializers.py