private void browseTreeForKeywords(Tree t) {
		if (t == null) {
			return;
		}
		if (t.type == NodeType.token) {
			if (Character.isLetter(t.node.charAt(1))) {
				keywords.add(t.node.substring(1, t.node.length() - 1));
			}
		}
		for (Tree b : t.branches) {
			browseTreeForKeywords(b);
		}
	}