Publish SNS message with AWS CLI including attributes

What is the correct syntax to include message attributes when publishing a message to an SNS topic? I know it's --message-attributes, but how to properly pass the values?

For example, to send a message I use this command line:

aws sns publish --topic-arn "arn:aws:sns:us-east-1:09706xxxxxxx:UpdatesTopic" --message "Update 1"

I want to include these message attributes:

MessageAttributes={
            'type': {
                'DataType': 'String',
                'StringValue': 'event_type_a'
            },
            'srcArn': {
                'DataType': 'String',
                'StringValue': f'arn:aws:ec2:us-east-1:09706xxxxxxx:instance/instance_a'
            },
            'session_id': {
                'DataType': 'String',
                'StringValue': 'abc123'
            },
            'owner': {
                'DataType': 'String',
                'StringValue': 'me'
            }
        }

You could use:

aws sns publish --topic-arn "arn:aws:sns:us-east-1:09706xxxxxxx:UpdatesTopic" --message "hello" --message-attributes '{"type":{"DataType":"String","StringValue":"event_type_a"},"srcArn":{"DataType":"String","StringValue":"arnxxx"}}'

or even:

aws sns publish --topic-arn "arn:aws:sns:us-east-1:09706xxxxxxx:UpdatesTopic" --message "hello" --message-attributes '
{
    "type": {
        "DataType": "String",
        "StringValue": "event_type_a"
    },
    "srcArn": {
        "DataType": "String",
        "StringValue": "arnxxx"
    }
}

This worked on a Mac. If you use Windows, then you might need to change your handling of quotation marks.