Constructs a new AWS access control policy condition that allows an
            access control statement to restrict subscriptions to an Amazon SNS topic
            based on the protocol being used for the subscription. For example, this
            condition can restrict subscriptions to a topic to endpoints using HTTPS
            to ensure that messages are securely delivered.
            
 Parameters
 Parameters- protocol (String)
- The protocol against which to compare the requested protocol for an Amazon SNS topic subscription.
 Return Value
 Return ValueA new access control policy condition that compares the
                    notification protocol requested in a request to subscribe to an
                    Amazon SNS topic with the protocol value specified.