code: public void setDataUsage(String activity, Map<String, Set<DataUsage>> dataUsage) throws PropertyException {
          Validate.notNull(activity);
          Validate.notEmpty(activity);
          Validate.notNull(dataUsage);
          Validate.noNullElements(dataUsage.keySet());
          Validate.noNullElements(dataUsage.values());
  
  		//1. Add data usages
          //   This also adds the data usages to the list of data usages
          List<String> propertyNamesForDataUsages = new ArrayList<>();
          for (String attribute : dataUsage.keySet()) {
              propertyNamesForDataUsages.add(addDataUsage(attribute, dataUsage.get(attribute)));
          }
  
          //2. Add data usage names to the list of data usages for this activity
          addActivityWithDataUsage(activity);
          props.setProperty(String.format(ACTIVITY_DATA_USAGES_FORMAT, activity), ArrayUtils.toString(propertyNamesForDataUsages.toArray()));
      }
docs: Data Usage