code: public DescribeRdsDbInstancesResult withRdsDbInstances(RdsDbInstance... rdsDbInstances) {
          if (this.rdsDbInstances == null) {
              setRdsDbInstances(new com.amazonaws.internal.SdkInternalList<RdsDbInstance>(rdsDbInstances.length));
          }
          for (RdsDbInstance ele : rdsDbInstances) {
              this.rdsDbInstances.add(ele);
          }
          return this;
      }
docs: <p>
  An a array of <code>RdsDbInstance</code> objects that describe the instances.
  </p>
  <p>
  <b>NOTE:</b> This method appends the values to the existing list (if any). Use
  {@link #setRdsDbInstances(java.util.Collection)} or {@link #withRdsDbInstances(java.util.Collection)} if you want
  to override the existing values.
  </p>
  
  @param rdsDbInstances
  An a array of <code>RdsDbInstance</code> objects that describe the instances.
  @return Returns a reference to this object so that method calls can be chained together.