code: private void checkJsdocInfoContainsObjectWithBadKey(Node n) {
      if (n.getJSDocInfo() != null) {
        JSDocInfo info = n.getJSDocInfo();
        checkTypeContainsObjectWithBadKey(n, info.getType());
        checkTypeContainsObjectWithBadKey(n, info.getReturnType());
        checkTypeContainsObjectWithBadKey(n, info.getTypedefType());
        for (String param : info.getParameterNames()) {
          checkTypeContainsObjectWithBadKey(n, info.getParameterType(param));
        }
      }
    }
docs: Checks if current node contains js docs and checks all types specified in the js doc whether
  they have Objects with potentially invalid keys. For example: {@code Object<!Object, number>}.
  If such type is found, a warning is reported for the current node.