protected function refreshToken(string $user): Slice
    {
        /**
         * @var $token Slice
         */
        $token = $this->tokens[$user];

        return $this->tokens[$user] = $this->authorize($user, [
            'grant_type'    => 'refresh_token',
            'refresh_token' => $token->getRequired('refresh_token'),
        ]);
    }
protected function refreshToken(string $user): Slice
    {
        /**
         * @var $token Slice
         */
        $token = $this->tokens[$user];

        return $this->tokens[$user] = $this->authorize($user, [
            'grant_type'    => 'refresh_token',
            'refresh_token' => $token->getRequired('refresh_token'),
        ]);
    }
@param string $user

@return Slice

@throws Invalid