How can I remove the key from fluent-bit output?

Question

I am using the following input in fluent-bit configuration of Kubernetes ConfigMap (YAML):

    [INPUT]
        Name          mem
        Tag           memory_usage
        Interval_Sec  60
        Interval_NSec 0

which provides output like:

{
    "_aws": {
        "Timestamp": 1617303986000,
        "CloudWatchMetrics": [
            {
                "Namespace": "fluent-bit-metrics",
                "Dimensions": [],
                "Metrics": [
                    {
                        "Name": "Mem.total",
                        "Unit": "Bytes"
                    },
                    {
                        "Name": "Mem.used",
                        "Unit": "Bytes"
                    },
                    {
                        "Name": "Mem.free",
                        "Unit": "Bytes"
                    },
                    {
                        "Name": "Swap.total",
                        "Unit": "Bytes"
                    },
                    {
                        "Name": "Swap.used",
                        "Unit": "Bytes"
                    },
                    {
                        "Name": "Swap.free",
                        "Unit": "Bytes"
                    }
                ]
            }
        ]
    },
    "Mem.total": 32676948,
    "Mem.used": 25955580,
    "Mem.free": 6721368,
    "Swap.total": 0,
    "Swap.used": 0,
    "Swap.free": 0
}

I am trying to remove _aws key and all its values by using this filter, but no success:

    [FILTER]
        Name record_modifier
        Match *
        Remove_key _aws

Can you suggest something with this issue?