code: func (n *cachedNode) rlp() []byte {
  	if node, ok := n.node.(rawNode); ok {
  		return node
  	}
  	blob, err := rlp.EncodeToBytes(n.node)
  	if err != nil {
  		panic(err)
  	}
  	return blob
  }
docs: // rlp returns the raw rlp encoded blob of the cached node, either directly from
  // the cache, or by regenerating it from the collapsed node.