code: public DescribePlacementGroupsResult withPlacementGroups(PlacementGroup... placementGroups) {
          if (this.placementGroups == null) {
              setPlacementGroups(new com.amazonaws.internal.SdkInternalList<PlacementGroup>(placementGroups.length));
          }
          for (PlacementGroup ele : placementGroups) {
              this.placementGroups.add(ele);
          }
          return this;
      }
docs: <p>
  Information about the placement groups.
  </p>
  <p>
  <b>NOTE:</b> This method appends the values to the existing list (if any). Use
  {@link #setPlacementGroups(java.util.Collection)} or {@link #withPlacementGroups(java.util.Collection)} if you
  want to override the existing values.
  </p>
  
  @param placementGroups
  Information about the placement groups.
  @return Returns a reference to this object so that method calls can be chained together.