/**
 * Implements hook_file_mimetype_mapping_alter().
 */
function {{ machine_name }}_file_mimetype_mapping_alter(&$mapping) {
  // Add new MIME type 'drupal/info'.
  $mapping['mimetypes']['example_info'] = 'drupal/info';
  // Add new extension '.info' and map it to the 'drupal/info' MIME type.
  $mapping['extensions']['info'] = 'example_info';
  // Override existing extension mapping for '.ogg' files.
  $mapping['extensions']['ogg'] = 189;
}
