code: protected static Container register(final DockerConfig config) {
          CONTAINERS_LOCK.lock();
          try {
              final String name = config.getName();
              Container container = CONTAINERS.get(name);
              if (container == null) {
                  container = new Container(config);
                  CONTAINERS.put(name, container);
              }
              LOGGER.info("Registered docker configuration: {}", name);
              return container;
          } finally {
              CONTAINERS_LOCK.unlock();
          }
      }
docs: Returns a {@link Container} for the given {@link DockerConfig}. If the container has not been
  created yet, this method will create it; otherwise, it will return the previously created
  container. There is a single <code>Container</code> associated with any given
  <code>DockerConfig</code>.
  
  @param config
  container configuration.
  @return a {@link Container} for the given {@link DockerConfig}.