public function initializeArguments()
{
$this->registerArgument('email', 'string', 'Email address', true);
$this->registerArgument('size', 'integer', 'Size in pixels, defaults to 80px [ 1 - 2048 ]', false);
$this->registerArgument('imageSet', 'string', 'Default image set to use. Possible values [ 404 | mm | identicon | monsterid | wavatar ] ', false);
$this->registerArgument('maximumRating', 'string', 'Maximum rating (inclusive) [ g | pg | r | x ]', false);
$this->registerArgument('secure', 'boolean', 'If it is FALSE will return the un secure Gravatar domain (www.gravatar.com)', false, true);
}