code: private static String serializeVariantSets(Map<String, VariantSet> map) {
  		StringBuilder result = new StringBuilder();
  
  		for (Entry<String, VariantSet> entry : map.entrySet()) {
  			result.append(entry.getKey()).append(":");
  			VariantSet variantSet = (VariantSet) entry.getValue();
  			result.append(variantSet.getDefaultVariant()).append(":");
  			result.append(getCommaSeparatedString(variantSet));
  			result.append(";");
  		}
  
  		return result.toString();
  	}
docs: Serialize the variant sets.
  
  @param map
  the map to serialize
  @return the serialized variant sets