def do_claim(self):
if self.__num_children == <NUM_LIT:1>:<EOL><INDENT>return next(iter(self.__children)).claimed_size<EOL><DEDENT>else:<EOL><INDENT>raise NotImplementedError<EOL><DEDENT>
Return the minimum width and height needed to render this widget.

Most widgets need to implement this method.  The exception is widgets 
that have exactly one child.  In that case, there's a reasonable 
default: claim just enough space for that child.   Most composite 
widgets are covered by this default, because they typically have a 
container widget as their only child and attach any other widgets they 
need to that container.