Returns this Item Thumbnails. Thumbnails are not supported on
        SharePoint Server 2016.

        :param size: request only the specified size: ej: "small",
         Custom 300x400 px: "c300x400", Crop: "c300x400_Crop"
        :return: Thumbnail Data
        :rtype: dict

def get_thumbnails(self, size=None):
        """ Returns this Item Thumbnails. Thumbnails are not supported on
        SharePoint Server 2016.

        :param size: request only the specified size: ej: "small",
         Custom 300x400 px: "c300x400", Crop: "c300x400_Crop"
        :return: Thumbnail Data
        :rtype: dict
        """
        if not self.object_id:
            return []

        url = self.build_url(
            self._endpoints.get('thumbnails').format(id=self.object_id))

        params = {}
        if size is not None:
            params['select'] = size

        response = self.con.get(url, params=params)
        if not response:
            return []

        data = response.json()

        if not self.thumbnails or size is None:
            self.thumbnails = data

        return data