code: public final Node clonePropsFrom(Node other) {
      checkState(this.propListHead == null, "Node has existing properties.");
      this.propListHead = other.propListHead;
      return this;
    }
docs: Clone the properties from the provided node without copying
  the property object.  The receiving node may not have any
  existing properties.
  @param other The node to clone properties from.
  @return this node.