How to deduplicate messages by ID in Python

import time

class MessageStore:
    def __init__(self):
        self.seen_ids = set()
        self.messages = {}
    
    def add(self, message_id, content, timestamp=None):
        timestamp = timestamp or time.time()
        if message_id in self.seen_ids:
            return False
        self.seen_ids.add(message_id)
        self.messages[message_id] = {"content": content, "received_at": timestamp}
        return True
    
    def get(self, message_id):
        return self.messages.get(message_id)
    
    def count(self):
        return len(self.seen_ids)


if __name__ == "__main__":
    store = MessageStore()
    
    # Simulate incoming messages
    test_messages = [
        ("msg_001", "Hello world"),
        ("msg_002", "Second message"),
        ("msg_001", "Duplicate attempt"),
        ("msg_003", "Third message"),
        ("msg_002", "Another duplicate"),
    ]
    
    for mid, text in test_messages:
        result = store.add(mid, text)
        status = "added" if result else "duplicate skipped"
        print(f"{mid}: {status}")
    
    print(f"Total unique messages: {store.count()}")
    print(f"Retrieved msg_001: {store.get('msg_001')}")