how can fetch all emails

Question

I use contextio for fetch all email of my account but I haven't fetch any email

this is code:

$args = array('label' => 'Primary','folder' => 'Inbox');
    $r = $contextio->listMessages('5a7364c56d5d992d945d54c3', $args);
    if ($r !== false) {
        foreach ($r->getData() as $message) {
            echo "Subject: ".$message['subject']."<br>";
        }
    } else {
        var_dump($r);
    }

output is false (in case else)