Using the most recent version of LocalStack and the most recent version of the AWS CLI...

```
awslocal sqs create-queue --queue-name foo                                                                                                                                                                         
{                                                                                                                                                                                                                  
    "QueueUrl": "http://localhost:4566/000000000000/foo"
} 

awslocal sqs send-message --message-body hello --queue-url http://localhost/000000000000/foo                                                                                                                       
{                                                                                                                                                                                                                  
  "MD5OfMessageBody": "5d41402abc4b2a76b9719d911017c592", 
  "MessageId": "53be5840-770a-49e6-8e23-cfca3469c7ff" 
}
                                                                                                                                                                                                                                                                                                              
awslocal sqs receive-message --queue-url http://localhost/000000000000/foo
{
   "Messages": [                                                                                                                                                                                                  
        {                                                                                                                                                                                                          
            "MessageId": "53be5840-770a-49e6-8e23-cfca3469c7ff",                                                                                                                                                   
            "ReceiptHandle": "ZmE3NTAxZjItZTEzMS00ZDNjLWE0ODgtODUzNTU0ZjE4YzBjIGFybjphd3M6c3FzOnVzLWVhc3QtMTowMDAwMDAwMDAwMDA6Zm9vIDUzYmU1ODQwLTc3MGEtNDllNi04ZTIzLWNmY2EzNDY5YzdmZiAxNjk4OTUwNjM2LjQxODc3ODc=",   
            "MD5OfBody": "5d41402abc4b2a76b9719d911017c592",                                                                                                                                                       
            "Body": "hello"                                                                                                                                                                                        
        }                                                                                                                                                                                                          
    ]                                                                                                                                                                                                              
}                                                                                                                                                                                                                  

awslocal sqs change-message-visibility --visibility-timeout 10 --queue-url http://localhost:4566/000000000000/foo --receipt-handle ZmE3NTAxZjItZTEzMS00ZDNjLWE0ODgtODUzNTU0ZjE4YzBjIGFybjphd3M6c3FzOnVzLWVhc3QtMTo\wMDAwMDAwMDAwMDA6Zm9vIDUzYmU1ODQwLTc3MGEtNDllNi04ZTIzLWNmY2EzNDY5YzdmZiAxNjk4OTUwNjM2LjQxODc3ODc=                                                                                                                  
                                                                                                                                                                                                                   
An error occurred (AWS.SimpleQueueService.MessageNotInflight) when calling the ChangeMessageVisibility operation: Unknown 
```
n = 0
        for message_group in self.message_groups.values():
            n += len(message_group.messages)
        return n
    def get_message_group(self, message_group_id: str) -> MessageGroup:
        """
        Thread safe lazy factory for MessageGroup objects.
        :param message_group_id: the message group ID
        :return: a new or existing MessageGroup object
        """
        with self.mutex:
            if message_group_id not in self.message_groups:
                # a 
                message_group = self.message_groups[message_group_id] = MessageGroup(
                    message_group_id
                )
                self.message_group_queue.put_nowait(message_group)
            return self.message_groups.get(message_group_id)
    def default_attributes(self) -> QueueAttributeMap:
        return {
            **super().default_attributes(),
            QueueAttributeName.ContentBasedDeduplication: "false",
            QueueAttributeName.DeduplicationScope: "queue",
            QueueAttributeName.FifoThroughputLimit: "perQueue",
        }
    def update_delay_seconds(self, value: int):
        super(FifoQueue, self).update_delay_seconds(value)
        for message in self.delayed:
            message.delay_seconds = value
    def remove(self, receipt_handle: str):