docs: public List<AstNode> getChildrenForType( AstNode astNode,
                                               String nodeType ) {
          CheckArg.isNotNull(astNode, "astNode");
          CheckArg.isNotNull(nodeType, "nodeType");
  
          List<AstNode> childrenOfType = new ArrayList<AstNode>();
          for (AstNode child : astNode.getChildren()) {
              if (hasMixinType(child, nodeType)) {
                  childrenOfType.add(child);
              }
              List<AstNode> subChildrenOfType = getChildrenForType(child, nodeType);
              childrenOfType.addAll(subChildrenOfType);
          }
  
          return childrenOfType;
      }