AWS Lambda function

Hello.
Now I am developing AWS lambda function.

Detailed description follows as:

1. Coding in lambda that is selenium by python
2. This selenium goes to web site and login
3. Take screen shot in top page then paste it to google slide.

But now I have a problem in AWS lambda function invoking.
Error leads to:
{
"errorMessage": "Handler 'lambda_handler' missing on module 'lambda_function'",
"errorType": "Runtime.HandlerNotFound",
"requestId": "40476982-a55b-4859-baf0-336f3f49321d",
"stackTrace": []
}

_

I am looking for your help.
Thank you.