modules/node/views_handler_argument_node_type.inc

<?php
class views_handler_argument_node_type extends views_handler_argument {
  function construct() {
    parent::construct('type');
  }

  function summary_name($data) {
    return $this->node_type($data->{$this->name_alias});
  }

  function title() {
    return $this->node_type($this->argument);
  }

  function node_type($type) {
    $output = node_type_get_name($type);
    if (empty($output)) {
      $output = t('Unknown content type');
    }
    return check_plain($output);
  }
}