from typing import Protocol

class Notifier(Protocol):
    def send(self, message: str) -> str:
        ...

class SlackNotifier:
    def send(self, message: str) -> str:
        return f"Sent to Slack: {message}"
    
class EmailNotifier:
    def send(self, message: str) -> str:
        return f"Sent via Email: {message}"
    
def send_alert(notifier: Notifier, message: str) -> str:
    return notifier.send(message)

slack_notifier = SlackNotifier()
email_notifier = EmailNotifier()

print(send_alert(slack_notifier, "This is a test alert for Slack!"))
print(send_alert(email_notifier, "This is a test alert for Email!"))