public static APIBuffer apiStack() {
        return API_BUFFERS.get().push();
    }
Returns a thread-local {@link APIBuffer}, without resetting it. This
makes the APIBuffer work like a stack when used in nested API calls. The
user is responsible for resetting the {@link APIBuffer} to an appropriate
state before the nested call returns.

@see APIBuffer#pop
jme3-lwjgl3/src/main/java/com/jme3/lwjgl3/utils/APIUtil.java