Turning on debugmode in the plugin:
Code:
{'height': '100%',
'version': '1.1',
'xmlns:xlink': 'http://www.w3.org/1999/xlink',
'xmlns': 'http://www.w3.org/2000/svg',
'width': '100%',
'viewbox': '0 0 600 800',
'preserveaspectratio': 'xMidYMid meet'}
one can clearly see that the lowercase attributes are generated already by building the soup.