Considereu la definició de la classe @Tree@ de l’exercici anterior.
Feu ara que la classe sigui iterable redefinint el mètode @__iter__@ en
forma de generador. Aquest generador ha d’anar retornant el recorregut
en amplada de l’arbre.
About statements
The official statement of a problem is always the one
in the PDF document. The HTML version of the statement
is also given to help you, but may contain some content
that is not well displayed. In case of doubt, always use the PDF.