code: public static IssueCategoryRegistry instance(Context context)
      {
          IssueCategoryRegistry registry = (IssueCategoryRegistry) context.get(IssueCategoryRegistry.class);
          if (registry == null)
          {
              registry = new IssueCategoryRegistry();
              context.put(IssueCategoryRegistry.class, registry);
          }
          return registry;
      }
docs: Gets an instance of the {@link IssueCategoryRegistry} from a {@link Context}. Note that the context variable
  used might vary depending upon how this class is being used.
  
  In some cases, the Context might be a part of the {@link RuleLoaderContext}, so that this registry can be used
  during rule initialization. In other cases, it may be the {@link GraphRewrite} event's context.