A lambda function is invoked with the following test event json

{ 
    "date":"2024-05-17 13:14:15",
}

The lambda_handler transfers execution to an internal method including the context:

        return handler(event, context)

I added print(event) in the handler and it shows the event as empty:

def get_call_metrics(event, context):
    query_params = event.get('queryStringParameters', {})
    print("query_params", query_params)

In Cloudwatch:

query_params {}

So then how is this test event json supposed to be used/how does it work?