def get_ancestor_list(n)
      raise ArgumentError, "n must be greater or equal than zero" unless n >= 0

      return [] if n == 0 || number == 0
      parent = get_parent
      [parent] + parent.get_ancestor_list(n-1)
    end
def get_ancestor_list(n)
      raise ArgumentError, "n must be greater or equal than zero" unless n >= 0

      return [] if n == 0 || number == 0
      parent = get_parent
      [parent] + parent.get_ancestor_list(n-1)
    end
Return `n` ancestors of this block.

 @return [Array] array of ancestors in format of `[parent, parent.parent, ...]