Histogram metrics fail to parse out sum

[moogspike]

For a histogram metric

# TYPE envoy_listener_downstream_cx_length_ms histogram
envoy_listener_downstream_cx_length_ms_bucket{envoy_listener_address="0.0.0.0_8080",le="1800000"} 1057540
envoy_listener_downstream_cx_length_ms_bucket{envoy_listener_address="0.0.0.0_8080",le="3600000"} 1057540
envoy_listener_downstream_cx_length_ms_bucket{envoy_listener_address="0.0.0.0_8080",le="+Inf"} 1057761
envoy_listener_downstream_cx_length_ms_sum{envoy_listener_address="0.0.0.0_8080"} 49511759034.9499969482421875
envoy_listener_downstream_cx_length_ms_count{envoy_listener_address="0.0.0.0_8080"} 1057761

# TYPE envoy_listener_admin_downstream_cx_length_ms histogram
envoy_listener_admin_downstream_cx_length_ms_bucket{le="1800000"} 23228
envoy_listener_admin_downstream_cx_length_ms_bucket{le="3600000"} 23228
envoy_listener_admin_downstream_cx_length_ms_bucket{le="+Inf"} 23228
envoy_listener_admin_downstream_cx_length_ms_sum{} 10585574.25
envoy_listener_admin_downstream_cx_length_ms_count{} 23228

The use of a label in the _sum barfs the parsing

The two examples above result in the following parsed output

[
    {
        "name": "envoy_listener_downstream_cx_length_ms",
        "help": "",
        "type": "HISTOGRAM",
        "metrics": [
            {
                "buckets": {
                    "1800000": "1057540",
                    "3600000": "1057540",
                    "+Inf": "1057761"
                }
            }
        ]
    },
    {
        "name": "envoy_listener_admin_downstream_cx_length_ms",
        "help": "",
        "type": "HISTOGRAM",
        "metrics": [
            {
                "buckets": {
                    "1800000": "23228",
                    "3600000": "23228",
                    "+Inf": "23228"
                },
                "count": "23228",
                "sum": "10585574.25"
            }
        ]
    }
]