knownValueMap.clear(); knownValueMap.putAll(replaceMap);
	public void mergeKnownValuesWith(IsNullValueFrame otherFrame) {		Map<ValueNumber, IsNullValue> replaceMap = new HashMap<ValueNumber, IsNullValue>();		for (Map.Entry<ValueNumber, IsNullValue> entry : knownValueMap.entrySet()) {			IsNullValue otherKnownValue = otherFrame.knownValueMap.get(entry.getKey());			if (otherKnownValue == null) {				continue;			}			replaceMap.put(entry.getKey(), IsNullValue.merge(entry.getValue(), otherKnownValue));		}	}