code: func (pdb *BytesBrokerWatcherEtcd) Delete(key string, opts ...datasync.DelOption) (existed bool, err error) {
  	return deleteInternal(pdb.Logger, pdb.kv, pdb.opTimeout, key, opts...)
  }
docs: // Delete calls 'Delete' function of the underlying BytesConnectionEtcd.
  // KeyPrefix defined in constructor is prepended to the key argument.