How to statically type Dynamo db in python?

I installed boto3 and has got the following code:

import boto3

def createProductsTable(db: DynamoDB.ServiceResource = None):
    if not db:
        db = boto3.resource('dynamodb', endpoint_url = 'http://localhost:8000')

I want my db parameter statically typed, but problem is that DynamoDB.ServiceResource object cannot be found in python library package! in "\site-packages\boto3\dynamodb..."

So, where is the object assumed to be stored??