code: public static void registerImplementation(Class<? extends ActionBarSherlock> implementationClass) {
          if (!implementationClass.isAnnotationPresent(Implementation.class)) {
              throw new IllegalArgumentException("Class " + implementationClass.getSimpleName() + " is not annotated with @Implementation");
          } else if (IMPLEMENTATIONS.containsValue(implementationClass)) {
              if (DEBUG) Log.w(TAG, "Class " + implementationClass.getSimpleName() + " already registered");
              return;
          }
  
          Implementation impl = implementationClass.getAnnotation(Implementation.class);
          if (DEBUG) Log.i(TAG, "Registering " + implementationClass.getSimpleName() + " with qualifier " + impl);
          IMPLEMENTATIONS.put(impl, implementationClass);
      }
docs: Register an ActionBarSherlock implementation.
  
  @param implementationClass Target implementation class which extends
  {@link ActionBarSherlock}. This class must also be annotated with
  {@link Implementation}.