Update collection documentation for specifying document IDs (#1211)
Update collection documentation for specifying document IDs (#1211)


googleapis/google-cloud-php,chingor13/google-cloud-php,jdpedrie/google-cloud-php,chingor13/google-cloud-php,googleapis/google-cloud-php,googleapis/google-cloud-php,chingor13/google-cloud-php,jdpedrie/google-cloud-php,jdpedrie/google-cloud-php