code: @Override
  	public final Map<String, String> toProperties() {
  		final DescriptorProperties properties = new DescriptorProperties();
  		properties.putProperties(internalProperties);
  
  		properties.putInt(STATISTICS_PROPERTY_VERSION, 1);
  
  		List<Map<String, String>> namedStats = new ArrayList<>();
  		for (Map.Entry<String, Map<String, String>> entry : columnStats.entrySet()) {
  			Map<String, String> columnStat = entry.getValue();
  			columnStat.put(NAME, entry.getKey());
  			namedStats.add(columnStat);
  		}
  
  		properties.putIndexedVariableProperties(STATISTICS_COLUMNS, namedStats);
  		return properties.asMap();
  	}
docs: Converts this descriptor into a set of properties.