code: public GetUsagePlanResult withApiStages(ApiStage... apiStages) {
          if (this.apiStages == null) {
              setApiStages(new java.util.ArrayList<ApiStage>(apiStages.length));
          }
          for (ApiStage ele : apiStages) {
              this.apiStages.add(ele);
          }
          return this;
      }
docs: <p>
  The associated API stages of a usage plan.
  </p>
  <p>
  <b>NOTE:</b> This method appends the values to the existing list (if any). Use
  {@link #setApiStages(java.util.Collection)} or {@link #withApiStages(java.util.Collection)} if you want to
  override the existing values.
  </p>
  
  @param apiStages
  The associated API stages of a usage plan.
  @return Returns a reference to this object so that method calls can be chained together.