When inserting multiple entities, creating a set of keys at once can be
useful. By defining the Key's kind and any ancestors up front, and
allowing Cloud Datastore to allocate IDs, you can be sure that your
entity identity and ancestry are correct and that there will be no
collisions during the insert operation.
Example:
$keys = $datastore->keys('Person', [
'number' => 10
]);
Ancestor paths can be specified
$keys = $datastore->keys('Person', [
'ancestors' => [
['kind' => 'Person', 'name' => 'Grandpa Joe'],
['kind' => 'Person', 'name' => 'Dad Mike']
],
'number' => 3
]);
