code: public void prependParentPath(final Map<Integer, String> parent_path) {
      if (parent_path == null) {
        throw new IllegalArgumentException("Parent path was null");
      }
      path = new TreeMap<Integer, String>();
      path.putAll(parent_path);
    }
docs: Sets the path for this branch based off the path of the parent. This map
  may be empty, in which case the branch is considered a root.
  <b>Warning:</b> If the path has already been set, this will create a new
  path, clearing out any existing entries
  @param parent_path The map to store as the path
  @throws IllegalArgumentException if the parent path is null