public JobNode getSeriesElement(int index) {
		return null;
	}
For nodes representing a flow or a split, return a specific element in the
series of things that will run either sequentially or in parallel.

@param index the element of interest
@return the indicated series or null if this is not a flow/split node
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/job/dsl/JobNode.java