@Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("{");
    if (defaultVersionTag != null) {
      sb.append("default = ").append(defaultVersionTag);
    }
    if (!configGroupOverrides.isEmpty()) {
      sb.append(", overrides = [ ");
      int i = 0;
      for (Map.Entry<Long, String> entry : configGroupOverrides.entrySet()) {
        if (i++ != 0) {
          sb.append(", ");
        }
        sb.append(entry.getKey()).append(" : ").append(entry.getValue());
      }
      sb.append("]");
    }
    sb.append("}");

    return sb.toString();
  }
Data structure that hangs off of the Host and points to what tags are
applicable to a config derived at the host-level
ambari-server/src/main/java/org/apache/ambari/server/state/HostConfig.java