pygtk problems with texttag widget

[zimio]

I write this code in my program:

buffer = self.log_textview.get_buffer()
tagtable = buffer.get_tag_table()
tag = tagtable.lookup('comment')
print tag.invisible

And then I get

AttributeError: 'gtk.TextTag' object has no attribute 'invisible'



But in the documentation it says that it does have that attribute...
http://www.pygtk.org/docs/pygtk/class-gtktexttag.html

What's the problem?

Thanks in advance.