code: func buildConfig(ctx *cli.Context) (config *bzzapi.Config, err error) {
  	//start by creating a default config
  	config = bzzapi.NewConfig()
  	//first load settings from config file (if provided)
  	config, err = configFileOverride(config, ctx)
  	if err != nil {
  		return nil, err
  	}
  	//override settings provided by environment variables
  	config = envVarsOverride(config)
  	//override settings provided by command line
  	config = cmdLineOverride(config, ctx)
  	//validate configuration parameters
  	err = validateConfig(config)
  
  	return
  }
docs: //before booting the swarm node, build the configuration