+ """ inserts <tagname> for every occurence of `split_re' in text nodes in the `doc' tree
+
+ >>> t = etree.fromstring('<a><b>A-B-C</b>X-Y-Z</a>');
+ >>> insert_tags(t, re.compile('-'), 'd');
+ >>> print etree.tostring(t)
+ <a><b>A<d/>B<d/>C</b>X<d/>Y<d/>Z</a>
+ """
+