code: public boolean unregisterSlotRequest(AllocationID allocationId) {
  		checkInit();
  
  		PendingSlotRequest pendingSlotRequest = pendingSlotRequests.remove(allocationId);
  
  		if (null != pendingSlotRequest) {
  			LOG.debug("Cancel slot request {}.", allocationId);
  
  			cancelPendingSlotRequest(pendingSlotRequest);
  
  			return true;
  		} else {
  			LOG.debug("No pending slot request with allocation id {} found. Ignoring unregistration request.", allocationId);
  
  			return false;
  		}
  	}
docs: Cancels and removes a pending slot request with the given allocation id. If there is no such
  pending request, then nothing is done.
  
  @param allocationId identifying the pending slot request
  @return True if a pending slot request was found; otherwise false