code: @Override
      public ModifyInstanceGroupsResult modifyInstanceGroups(ModifyInstanceGroupsRequest request) {
          request = beforeClientExecution(request);
          return executeModifyInstanceGroups(request);
      }
docs: <p>
  ModifyInstanceGroups modifies the number of nodes and configuration settings of an instance group. The input
  parameters include the new target instance count for the group and the instance group ID. The call will either
  succeed or fail atomically.
  </p>
  
  @param modifyInstanceGroupsRequest
  Change the size of some instance groups.
  @return Result of the ModifyInstanceGroups operation returned by the service.
  @throws InternalServerErrorException
  Indicates that an error occurred while processing the request and that the request was not completed.
  @sample AmazonElasticMapReduce.ModifyInstanceGroups
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/elasticmapreduce-2009-03-31/ModifyInstanceGroups"
  target="_top">AWS API Documentation</a>