'Calls ``method`` on every member of the subtree
:param method: method
:type  method: str'

def broadcast(self, method, *args, **kwargs):

    if hasattr(self, method):
        getattr(self, method)(*args, **kwargs)
    if (not self.visible):
        return
    for child in self.children:
        child.broadcast(method, *args, **kwargs)
