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: manifold.go
    path of file: ./repos/juju/worker/instancepoller
    
    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 instancepoller

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

	"github.com/juju/juju/api/base"
	"github.com/juju/juju/api/contr
    
func (config ManifoldConfig) start(context dependency.Context) (worker.Worker, error) {
	var clock clock.Clock
	if err := context.Get(config.ClockName, &clock); err != nil {
		return nil, errors.Trace(err)
	}
	var environ environs.Environ
	if err := context.Get(config.EnvironName, &environ); err != nil {
		return nil, errors.Trace(err)
	}

	// If the current environment does not support networking use a shim
	// whose NetworkInterfaces method always returns a NotSupported error.
	netEnv, supported := environ.(Environ)
	if !supported {
		netEnv = &environWithoutNetworking{env: environ}
	}

	var apiCaller base.APICaller
	if err := context.Get(config.APICallerName, &apiCaller); err != nil {
		return nil, errors.Trace(err)
	}

	credentialAPI, err := config.NewCredentialValidatorFacade(apiCaller)
	if err != nil {
		return nil, errors.Trace(err)
	}

	w, err := NewWorker(Config{
		Clock: clock,
		Facade: facadeShim{
			api: instancepoller.NewAPI(apiCaller),
		},
		Environ:       netEnv,
		Logger:        config.Logger,
		CredentialAPI: credentialAPI,
	})
	if err != nil {
		return nil, errors.Trace(err)
	}
	return w, nil
}