xml problem in parsing the great grandchildren

import xml.etree.ElementTree as ET

inv = open('lshw.xml', 'r')
inv = inv.read()
inv = ET.XML(inv)

find_memory =inventory.findall(".//node[@id='bank:*']")

# I am stuck here. What is required is description of the system memory, but system has lot of places where class=memory is used and hence i can't use it. i need the one's which has id=bank:0 .. n and collect the decryption of it.