code: public ParseTreeNode getChild(String name) throws TreeException {
  	ParseTreeNode result = null;
  	for (ParseTreeNode child : children) {
  	    if (child.getName().equals(name)) {
  		if (result != null) {
  		    throw new TreeException("Child '" + name + "'is multiply defined!");
  		}
  		result = child;
  	    }
  	}
  	return result;
      }
docs: This method returns the child with the given name from this node.
  
  It is used to extract exactly one child from this node. To get more children,
  use {@link #getChildren()} for that purpose.
  
  @param name
  is the name of the child.
  @return The child is returned if found. Otherwise null is returned.
  @throws TreeException
  is thrown if there is more than one child with the given name.