code: private JsonObject resolve(JsonObject node, String ...keys) {
      for (String key : keys) {
        JsonElement n = node.get(key);
        if (n == null) {
          return null;
        }
        node = n.getAsJsonObject();
      }
      return node;
    }
docs: Recursively resolve a series of keys against a JSON object. This is used to
  drill down into a JSON object tree.