Add the specified key / data pair to this list at the specified level, and load into the specified result a reference to the pair in the list. The result reference must be released (using releaseReferenceRaw) when it is no longer needed. Load into the the optionally specified newFrontFlag a true value if the pair is at the front of the list, and a false value otherwise. The behavior is undefined if level is greater than the implementation-defined maximum level of this class, or if level is negative. Return 0 on success, and a non-zero value (with no effect on the list) if key is already in the list. Note that this method is provided for testing purposes.