code: public synchronized ContainerShutdownDescriptor removeContainer(String containerId) {
          ContainerShutdownDescriptor descriptor = shutdownDescriptorPerContainerMap.remove(containerId);
          if (descriptor != null) {
              removeContainerIdFromLookupMaps(containerId);
              removeDescriptorFromPomLabelMap(descriptor);
          }
          return descriptor;
      }
docs: Remove a container from this container (if stored) and return its descriptor
  
  @param containerId id to remove
  @return descriptor of the container removed or <code>null</code>