code: public Collection<SingularityRequestCleanup> getCleanupSingularityRequests() {
      final Function<String, String> requestUri = (host) -> String.format(REQUESTS_GET_CLEANUP_FORMAT, getApiBase(host));
  
      return getCollection(requestUri, "cleaning requests", CLEANUP_REQUESTS_COLLECTION);
    }
docs: Get all requests that are cleaning up
  Requests that are cleaning up are those that have been marked for removal and their tasks are being stopped/removed
  before they are being removed. So after their have been cleaned up, these request cease to exist in Singularity.
  
  @return
  A collection of {@link SingularityRequestCleanup} instances that hold information about all singularity requests
  that are marked for deletion and are currently cleaning up.