{
    "icon": "poi-fire-hydrant",
    "fields": [
        "fire_hydrant/type",
        "fire_hydrant/position"
    ],
    "geometry": [
        "point",
        "vertex"
    ],
    "terms": [
        "fire plug"
    ],
    "tags": {
        "emergency": "fire_hydrant"
    },
    "name": "Fire Hydrant"
}

{
    "icon": "poi-fire-hydrant",
    "fields": [
        "fire_hydrant/type",
        "fire_hydrant/position",
        "ref",
        "operator"
    ],
    "geometry": [
        "point",
        "vertex"
    ],
    "terms": [
        "fire plug"
    ],
    "tags": {
        "emergency": "fire_hydrant"
    },
    "name": "Fire Hydrant"
}

Add ref and operator to fire hydrant.
Add ref and operator to fire hydrant.