code: public void addPostProcessVariant(Map<String, VariantSet> variants) {
  
  		if (!searchingPostProcessorVariants) {
  			throw new BundlingProcessException(
  					"You are not allowed to define post process variants if we are not searching for post processor variants.");
  		}
  		postProcessVariants = VariantUtils.concatVariants(postProcessVariants, variants);
  	}
docs: Add a post process variant
  
  @param variants
  the variant map