code: public synchronized Collection<ContainerShutdownDescriptor> removeShutdownDescriptors(GavLabel gavLabel) {
          List<ContainerShutdownDescriptor> descriptors;
          if (gavLabel != null) {
              descriptors = removeFromPomLabelMap(gavLabel);
              removeFromPerContainerMap(descriptors);
          } else {
              // All entries are requested
              descriptors = new ArrayList<>(shutdownDescriptorPerContainerMap.values());
              clearAllMaps();
          }
  
          Collections.reverse(descriptors);
          return descriptors;
      }
docs: Get all shutdown descriptors for a given pom label and remove it from the tracker. The descriptors
  are returned in reverse order of their registration.
  
  If no pom label is given, then all descriptors are returned.
  
  @param gavLabel the label for which to get the descriptors or <code>null</code> for all descriptors
  @return the descriptors for the given label or an empty collection