Drupal drush template with argument and options

custom_module.drush.inc

<?php

/**
 * Implements hook_drush_command
 */
function custom_module_drush_command() {

  $items['drush-command'] = array(
    'description' => "This is a drush command.",
    'aliases' => array('dc'),
    'arguments' => array(
      'type' => 'Arguments need to be provided',
    ),
    'options' => array(
      'repeat' => 'Options do not need to be provided',
    ),
    'examples' => array(
      'drush drush-command' => 'Prints an error message',
      'drush drush-command success' => 'Prints a success message',
      'drush drush-command success --repeat=5' => 'Prints 5 success messages',
    ),
  );

  return $items;
}

function drush_custom_module_drush_command($type = 'error') {
  $validArgs = array('error', 'success');
  $repeat = drush_get_option('repeat', 1);

  if(is_numeric($repeat) && $repeat > 0) {
    for($i = 0; $i < $repeat; $i += 1) {
      drupal_set_message(t('Hello world! '), $type);
    }
  }
}