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: unitassigner.go
    path of file: ./repos/juju/worker/unitassigner
    
    the code of the file until where you have to start completion: // Copyright 2015 Canonical Ltd.
// Licensed under the AGPLv3, see LICENCE file for details.

package unitassigner

import (
	"github.com/juju/errors"
	"github.com/juju/names/v5"
	"github.com/juju/worker/v3"

	"github.com/juju/juju/core/status"
	"github.com/juju/juju/core/watcher"
	"github.com/juju/juju/rpc/params"
)

// logger is here to stop the desire of creating a package level logger.
// Don't do this, instead use th
    
func (u unitAssignerHandler) Handle(_ <-chan struct{}, ids []string) error {
	u.logger.Tracef("Handling unit assignments: %q", ids)
	if len(ids) == 0 {
		return nil
	}

	units := make([]names.UnitTag, len(ids))
	for i, id := range ids {
		if !names.IsValidUnit(id) {
			return errors.Errorf("%q is not a valid unit id", id)
		}
		units[i] = names.NewUnitTag(id)
	}

	results, err := u.api.AssignUnits(units)
	if err != nil {
		return err
	}

	failures := map[string]error{}

	u.logger.Tracef("Unit assignment results: %q", results)
	// errors are returned in the same order as the ids given. Any errors from
	// the assign units call must be reported as error statuses on the
	// respective units (though the assignments will be retried).  Not found
	// errors indicate that the unit was removed before the assignment was
	// requested, which can be safely ignored.
	for i, err := range results {
		if err != nil && !errors.IsNotFound(err) {
			failures[units[i].String()] = err
		}
	}

	if len(failures) > 0 {
		args := params.SetStatus{
			Entities: make([]params.EntityStatusArgs, len(failures)),
		}

		x := 0
		for unit, err := range failures {
			args.Entities[x] = params.EntityStatusArgs{
				Tag:    unit,
				Status: status.Error.String(),
				Info:   err.Error(),
			}
			x++
		}

		return u.api.SetAgentStatus(args)
	}
	return nil
}