code: private StartInstancesResponseType startInstances(final Set<String> instanceIDs) {
          StartInstancesResponseType ret = new StartInstancesResponseType();
          ret.setRequestId(UUID.randomUUID().toString());
          InstanceStateChangeSetType changeSet = new InstanceStateChangeSetType();
          changeSet.getItem().addAll(mockEc2Controller.startInstances(instanceIDs));
          ret.setInstancesSet(changeSet);
          return ret;
  
      }
docs: Handles "startInstances" request, with only a simplified filter of instanceIDs.
  
  @param instanceIDs
  a filter of specified instance IDs for the target instance to start
  @return a StartInstancesResponse with information for all mock ec2 instances to start