@Override
  public ScheduledFunction getScheduledFn() {
    return this.transformFn instanceof ScheduledFunction ? (ScheduledFunction) this.transformFn : null;
  }
The spec for an operator that transforms each input message to a collection of output messages.

@param <M> type of input message
@param <OM> type of output messages
samza-core/src/main/java/org/apache/samza/operators/spec/FlatMapOperatorSpec.java