Here is how I did it using python boto3.
from boto3 import client as boto3_client
from datetime import datetime
import json
lambda_client = boto3_client('lambda')
def lambda_handler(event, context):
msg = {"key":"new_invocation", "at": datetime.now()}
invoke_response = lambda_client.invoke(FunctionName="another_lambda_",
InvocationType='Event',
Payload=json.dumps(msg))
print(invoke_response)