@Override
  public String toString() {
    return "Container[" + getParentAccountId() + ":" + getId() + "]";
  }
Generates a String representation that uniquely identifies this container. The string
is in the format of {@code Container[accountId:containerId]}.
@return The String representation of this container.
ambry-api/src/main/java/com/github/ambry/account/Container.java