          info = modelinfo.get_field_info(self.opts.model)
          ret = OrderedDict()
  
          serializer_pk_field = self.get_pk_field(info.pk)
          if serializer_pk_field:
              ret[info.pk.name] = serializer_pk_field
  
          # Regular fields
          for field_name, field in info.fields.items():
 
</s> remove     def get_default_fields(self):
        fields = super(HyperlinkedModelSerializer, self).get_default_fields()

        if self.opts.view_name is None:
            self.opts.view_name = self.get_default_view_name(self.opts.model)

        url_field_name = api_settings.URL_FIELD_NAME
        if url_field_name not in fields:
            ret = fields.__class__()
            ret[url_field_name] = self.get_url_field()
            ret.update(fields)
            fields = ret

        return fields

    def get_pk_field(self, model_field):
        if self.opts.fields and model_field.name in self.opts.fields:
            return self.get_field(model_field)

 </s> add  </s> remove         # if issubclass(model_field.__class__, models.TextField):
        #     kwargs['widget'] = widgets.Textarea

        # if model_field.help_text is not None:
        #     kwargs['help_text'] = model_field.help_text

        # TODO: TypedChoiceField?
        if model_field.flatchoices:  # This ModelField contains choices
            kwargs['choices'] = model_field.flatchoices
            if model_field.null:
                kwargs['empty'] = None
            return ChoiceField(**kwargs)

        if model_field.null and \
                issubclass(model_field.__class__, (models.CharField, models.TextField)):
            kwargs['allow_none'] = True

 </s> add 
        serializer_url_field = self.get_url_field()
        if serializer_url_field:
            ret[api_settings.URL_FIELD_NAME] = serializer_url_field

          info = modelinfo.get_field_info(self.opts.model)
          ret = OrderedDict()
  
        serializer_url_field = self.get_url_field()
        if serializer_url_field:
            ret[api_settings.URL_FIELD_NAME] = serializer_url_field

          serializer_pk_field = self.get_pk_field(info.pk)
          if serializer_pk_field:
              ret[info.pk.name] = serializer_pk_field
  
          # Regular fields
          for field_name, field in info.fields.items():
keep keep add keep keep keep keep keep keep
 Added help_text argument to fields 
rest_framework/serializers.py