You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: strmap.go
    path of file: ./repos/mgmt/etcd/client/strmap
    
    the code of the file until where you have to start completion: // Mgmt
// Copyright (C) 2013-2024+ James Shubin and the project contributors
// Written by James Shubin <james@shubin.ca> and the project contributors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
// Additional permission under GNU GPL version 3 section 7
//
// If you modify this prog
    
func SetStrMap(ctx context.Context, client interfaces.Client, hostname, key string, data *string) error {
	// key structure is $NS/strings/$key/$hostname = $data
	path := fmt.Sprintf("%s/strings/%s/%s", ns, key, hostname)
	ifs := []etcd.Cmp{} // list matching the desired state
	ops := []etcd.Op{}  // list of ops in this transaction (then)
	els := []etcd.Op{}  // list of ops in this transaction (else)
	if data == nil {    // perform a delete
		ifs = append(ifs, etcdutil.KeyExists(path))
		//ifs = append(ifs, etcd.Compare(etcd.Version(path), ">", 0))
		ops = append(ops, etcd.OpDelete(path))
	} else {
		data := *data                                                // get the real value
		ifs = append(ifs, etcd.Compare(etcd.Value(path), "=", data)) // desired state
		els = append(els, etcd.OpPut(path, data))
	}

	// it's important to do this in one transaction, and atomically, because
	// this way, we only generate one watch event, and only when it's needed
	_, err := client.Txn(ctx, ifs, ops, els) // TODO: do we need to look at response?
	return errwrap.Wrapf(err, "could not set strings in: %s", key)
}