/**
 * Implements hook_tokens().
 */
function mymodule_tokens($type, $tokens, array $data = array(), array $options = array()) {
  $replacements = array();
  if ($type == 'key_token' && !empty($data['node'])) {
    $node = $data['node'];
    foreach ($tokens as $name => $original) {
      $replacements[$original]='Some_value';
      }
    }
  }
  return $replacements;
}