private void updatePomLabelMap(GavLabel gavLabel, ContainerShutdownDescriptor descriptor) {
        if (gavLabel != null) {
            List<ContainerShutdownDescriptor> descList = shutdownDescriptorPerPomLabelMap.get(gavLabel);
            if (descList == null) {
                descList = new ArrayList<>();
                shutdownDescriptorPerPomLabelMap.put(gavLabel, descList);
            }
            descList.add(descriptor);
        }
    }
Get all shutdown descriptors for a given pom label.
The descriptors are returned in 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
src/main/java/io/fabric8/maven/docker/service/ContainerTracker.java