code: public void walkSourceContents(SourceWalker walker) {
          for (int i = 0, len = this.children.size(); i < len; i++) {
              if (this.children.get(i) instanceof SourceNode) {
                  ((SourceNode) this.children.get(i)).walkSourceContents(walker);
              }
          }
  
          for (Entry<String, String> entry : this.sourceContents.entrySet()) {
              walker.walk(entry.getKey(), entry.getValue());
          }
      }
docs: Walk over the tree of SourceNodes. The walking function is called for each source file content and is passed the filename and source content.
  
  @param aFn
  The traversal function.