docs: def array(self,n=-1):
          """returns a numpy array created from the list that was closed last (if `n`=-1).
          If `n` is None, the lists of the current level are returned as an array.
          Other lists in the current level can also be accessed with `n` as the specific index.
          """
          if n is None:
              return np.array(self.list)
          return np.array(self.list)[n]