@Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("GetResponse[");
    if (toSend != null) {
      sb.append("SizeToSend=").append(toSend.sizeInBytes());
    }
    sb.append(" ServerErrorCode=").append(getError());
    if (partitionResponseInfoList != null) {
      sb.append(" PartitionResponseInfoList=").append(partitionResponseInfoList);
    }
    sb.append("]");
    return sb.toString();
  }
Override the release method from {@link RequestOrResponse}. When the {@link #prepareBuffer()} is not invoked, there
will be {@link #toSend}'s content waiting for releasing.
@return
ambry-protocol/src/main/java/com/github/ambry/protocol/GetResponse.java