Method readProduct returns None for Sentinel-3 product

I’m newbie in snapy, therefore for learning I use samples presented (among others) on this forum.
I’ve found simple code like this:
import snappy
import numpy as np

filename = '/eodata/Sentinel-3/SRAL/SR_2_LAN/2017/08/10/S3A_SR_2_LAN____20170810T021859_20170810T022700_20170810T032119_0481_021_032______SVL_O_NR_002.SEN3/xfdumanifest.xml'
prod = snappy.ProductIO.readProduct(filename)
#prod is None:(
width = int(prod.getSceneRasterWidth())
height = int(prod.getSceneRasterHeight())

but prod has None value and next lines return errors.
I’m sure file described by filename varialbe exists.
What is the problem (other products: e.g. sentinel-1 work).

Best regards,

S3 Altimetry products are not supported by SNAP, sorry. SNAP cannot read this data.

You can try BRAT. It’s available from here: