def do_regroup_children(self):
for child in self.__children:<EOL><INDENT>child._regroup(self.group)<EOL><DEDENT>
React to changes that might require this widget's children to be 
regrouped.

This method is called when the widget's own group is changed or when 
children are attached to or detached from the widget.  A typical 
implementation would iterate through all the children attached to the 
widget and call `_regroup()` on each one.  The default implementation 
puts all the children in the same group as the widget itself.