PHP Fatal error: Uncaught Error: Class 'Google_Service_PhotosLibrary' not found

[quantrpeter]

hi php 7.3 got "PHP Fatal error: Uncaught Error: Class 'Google_Service_PhotosLibrary' not found"

composer.json:

{
    "require": {
        "google/photos-library": "^1.7",
        "google/apiclient": "^2.14"
    }
}

please help thanks