protected void removeAlertGroup(AlertGroupEntity alertGroup) {
    if (null != alertGroups) {
      alertGroups.remove(alertGroup);
    }
  }
Removes the specified alert group to the groups that this target 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/AlertTargetEntity.java