code: InputSplit getInputSplitFromLog(final ExecutionVertex vertex, final int sequenceNumber) {
  
  		final List<InputSplit> inputSplitLog = this.splitMap.get(vertex.getID());
  		if (inputSplitLog == null) {
  			LOG.error("Cannot find input split log for vertex " + vertex + " (" + vertex.getID() + ")");
  			return null;
  		}
  
  		synchronized (inputSplitLog) {
  
  			if (sequenceNumber < inputSplitLog.size()) {
  				return inputSplitLog.get(sequenceNumber);
  			}
  		}
  
  		return null;
  	}
docs: Returns the input split with the given sequence number from the specified vertex's log or <code>null</code> if no
  such input split exists.
  
  @param vertex
  the vertex for which the input split shall be returned from the log
  @param sequenceNumber
  the sequence number identifying the log entry
  @return the input split that was stored under the given sequence number of the vertex's log or <code>null</code>
  if no such input split exists