def subtree_of?(parent_tree)
      parent_tree = make_object_id(parent_tree)
      if parent_tree.length > self.length
        false
      else
        parent_tree.each_index do |i|
          return false if parent_tree[i] != self[i]
        end
        true
      end
    end
def subtree_of?(parent_tree)
      parent_tree = make_object_id(parent_tree)
      if parent_tree.length > self.length
        false
      else
        parent_tree.each_index do |i|
          return false if parent_tree[i] != self[i]
        end
        true
      end
    end
Returns true if this ObjectId is a subtree of the provided parent tree
 ObjectId.  For example, "1.3.6.1.5" is a subtree of "1.3.6.1".