Services/Libravatar.php
protected function normalizeIdentifier($identifier)
    {
        if (filter_var($identifier, FILTER_VALIDATE_EMAIL)) {
            return strtolower($identifier);
        } else {
            return self::normalizeOpenId($identifier);
        }
    }
protected function normalizeIdentifier($identifier)
    {
        if (filter_var($identifier, FILTER_VALIDATE_EMAIL)) {
            return strtolower($identifier);
        } else {
            return self::normalizeOpenId($identifier);
        }
    }
Normalizes the identifier (E-mail address or OpenID)

@param string $identifier E-Mail address or OpenID

@return string Normalized identifier