code: private void toStringTree(String indent, StringBuffer sb) {
  		sb.append(toString());
  		if (children != null) {
  			for (Entry<String, DepTreeNode> entry : children.entrySet()) {
  				entry.getValue().toStringTree(indent + "\t", sb); //$NON-NLS-1$
  			}
  		}
  	}
docs: Prints the string representaton of the tree rooted at this node to the
  specified {@link StringBuffer}.
  
  @param indent
  String for indenting nodes
  @param sb
  The StringBuffer to output to