Error while adding openAI provider

Hello,

I'm trying this module. I stored a new OpenAI key, but when I added it and clicked on "Save Configuration," I got this error:

The website encountered an unexpected error. Try again later.
Error: Class "OpenAI" not found in Drupal\ai_provider_openai\Form\OpenAiConfigForm->validateForm() (line 106 of modules/ai_provider_openai/src/Form/OpenAiConfigForm.php).

thank you for your help