code: private Map<String, CompiledClass> extractClassFileMap() {
      if (context instanceof StandardGeneratorContext) {
        StandardGeneratorContext standardContext = (StandardGeneratorContext) context;
        return standardContext.getCompilationState().getClassFileMap();
      } else {
        logger.log(TreeLogger.Type.WARN,
            String.format("Could not load generated classes from GWT context, "
                + "encountered unexpected generator type %s.", context.getClass()));
        return null;
      }
    }
docs: Retrieves class definitions from a {@link GeneratorContext} by downcasting.