myfile.geojson

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {
        "x": "a"
      },
      "geometry": {
        "type": "MultiPoint",
        "coordinates": [
          [3.2, 4],
          [3, 4.6],
          [3.8, 4.4],
          [3.5, 3.8],
          [3.4, 3.6],
          [3.9, 4.5]
        ]
      }
    }
  ]
}