code: public final I getInvocation(Object protocolKey)
    {
      I invocation = null;
  
      // XXX: see if can remove this
      LruCache<Object,I> invocationCache = _invocationCache;
  
      if (invocationCache != null) {
        invocation = invocationCache.get(protocolKey);
      }
  
      if (invocation == null) {
        return null;
      }
      else if (invocation.isModified()) {
        return null;
      }
      else {
        return invocation;
      }
    }
docs: Returns the cached invocation.