def exportValue(self, vf, value):
        m = StrStrHashMap(value)
        keysAndValues = []
        for i in m.keys():
            keysAndValues.append(i)
            keysAndValues.append(m[i])
def _update_height(self, height_diff):
    if self._items_total_height is None:
      self._items_total_height = self.get_allocation().height