* is the only one in use, but if we encounter nested concatenations, we start a deque of
     * meta-iterators rather than letting the nesting get arbitrarily deep.  This keeps each
     * operation O(1).
     */

    private @Nullable Iterator<? extends Iterator<? extends T>> topMetaIterator;

    // Only becomes nonnull if we encounter nested concatenations.

                sb.append("]");
            }
            sb.append("; ");
            target = target.getCause();
            if (target != null) {
                sb.append("nested: ");
            }
        }
        return sb.toString();
    }

    /**
     * Processes a label request.
     * @param request The HTTP request.
     * @param response The HTTP response.

* kubectl now supports validation of nested objects with different ApiGroups (e.g. objects in a List) ([#25172](https://github.com/kubernetes/kubernetes/pull/25172), [@pwittrock](https://github.com/pwittrock))