code: func RunCompletion(out io.Writer, boilerPlate string, cmd *cobra.Command, args []string) error {
  	if len(args) == 0 {
  		return cmdutil.UsageErrorf(cmd, "Shell not specified.")
  	}
  	if len(args) > 1 {
  		return cmdutil.UsageErrorf(cmd, "Too many arguments. Expected only the shell type.")
  	}
  	run, found := completionShells[args[0]]
  	if !found {
  		return cmdutil.UsageErrorf(cmd, "Unsupported shell type %q.", args[0])
  	}
  
  	return run(out, boilerPlate, cmd.Parent())
  }
docs: // RunCompletion checks given arguments and executes command