code: def list(ctx, show_hidden, oath_type, period):
      
      ensure_validated(ctx)
      controller = ctx.obj['controller']
      creds = [cred
               for cred in controller.list()
               if show_hidden or not cred.is_hidden
               ]
      creds.sort()
      for cred in creds:
          click.echo(cred.printable_key, nl=False)
          if oath_type:
              click.echo(u', {}'.format(cred.oath_type.name), nl=False)
          if period:
              click.echo(', {}'.format(cred.period), nl=False)
          click.echo()
docs: List all credentials.
  
      List all credentials stored on your YubiKey.