>>> html2
<genshi.core.Stream object at 0xb7dba42c>
>>> print html2
<b>foo</b><i>fee</i>
>>> print html2 |  Transformer('//b').replace('replaced')
replaced<i>fee</i>
>>> print html2 |  Transformer('//b').substitute('f', 'g')
<b>goo</b><i>gee</i>