def index(self, item):
index_at = None<EOL>for (i, child) in enumerate(self._children):<EOL><INDENT>if child.item == item:<EOL><INDENT>index_at = i<EOL>break<EOL><DEDENT><DEDENT>if index_at is None:<EOL><INDENT>raise ValueError("<STR_LIT>" % (item))<EOL><DEDENT>return index_at<EOL>
Finds the child index of a given item, searchs in added order.