private void removeDescriptorFromPomLabelMap(ContainerShutdownDescriptor descriptor) {
        Iterator<Map.Entry<GavLabel, List<ContainerShutdownDescriptor>>> mapIt = shutdownDescriptorPerPomLabelMap.entrySet().iterator();
        while(mapIt.hasNext()) {
            Map.Entry<GavLabel,List<ContainerShutdownDescriptor>> mapEntry = mapIt.next();
            List<ContainerShutdownDescriptor> descs = mapEntry.getValue();
            Iterator<ContainerShutdownDescriptor> it = descs.iterator();
            while (it.hasNext()) {
                ContainerShutdownDescriptor desc = it.next();
                if (descriptor.equals(desc)) {
                    it.remove();
                }
            }
            if (descs.size() == 0) {
                mapIt.remove();
            }
        }
    }
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