protected void addAlertGroup(AlertGroupEntity alertGroup) {
    if (null == alertGroups) {
      alertGroups = new HashSet<>();
    }

    alertGroups.add(alertGroup);
  }
Adds the specified alert group to the groups that this definition is
associated with. This is used to complement the JPA bidirectional
association.

@param alertGroup
ambari-server/src/main/java/org/apache/ambari/server/orm/entities/AlertDefinitionEntity.java