code: public static String getIdentifier(final Configuration c) {
      try {
        return Tang.Factory.getTang().newInjector(c).getNamedInstance(
            ContextIdentifier.class);
      } catch (final InjectionException e) {
        throw new RuntimeException("Unable to determine context identifier. Giving up.", e);
      }
    }
docs: Extracts a context id from the given configuration.
  
  @param c
  @return the context id in the given configuration.
  @throws RuntimeException if the configuration can't be parsed.