code: @Override
    public int compareTo(Flow otherFlow) {
      if (otherFlow == null) {
        return -1;
      }
      return new CompareToBuilder().append(this.key, otherFlow.getFlowKey())
          .toComparison();
    }
docs: Compares two Flow objects on the basis of their FlowKeys
  
  @param otherFlow
  @return 0 if the FlowKeys are equal,
  1 if this FlowKey greater than other FlowKey,
  -1 if this FlowKey is less than other FlowKey