public CallStack addAfter(Call after, CallStack callStack) {
        int insertPosition = elements.indexOf(after);
        if (insertPosition < 0) {
            addLast(callStack);
        } else {
            elements.addAll(insertPosition + 1, callStack.elements);
        }
        return this;
    }
Adds multiple elements just after another given element on the stack.
This can not be called during an iteration.

@param after the call to add this before. If this call is not present, (the
             same object instance), the new processor is added as the last element
@param callStack the calls to add
@return this for convenience
docproc/src/main/java/com/yahoo/docproc/CallStack.java