code: def apply_saved_layout(self):
          
          num_widgets = self.config.get(self.config_key + "/num_widgets", int)
          if num_widgets:
              sizes = []
              for i in range(num_widgets):
                  key = "%s/size_%d" % (self.config_key, i)
                  size = self.config.get(key, int)
                  sizes.append(size)
              self.setSizes(sizes)
              return True
          return False
docs: Call this after adding your child widgets.