myfile.geojson

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {
        "x": "a"
      },
      "geometry": {
        "type": "GeometryCollection",
        "geometries": [
          {
            "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]
            ]
          },
          {
            "type": "MultiPolygon",
            "coordinates": [
              [
                [
                  [0, 0],
                  [1, 0],
                  [3, 2],
                  [2, 4],
                  [1, 4],
                  [0, 0]
                ],
                [
                  [1, 1],
                  [1, 2],
                  [2, 2],
                  [1, 1]
                ]
              ],
              [
                [
                  [3, 0],
                  [4, 0],
                  [4, 1],
                  [3, 1],
                  [3, 0]
                ],
                [
                  [3.3, 0.3],
                  [3.3, 0.8],
                  [3.8, 0.8],
                  [3.8, 0.3],
                  [3.3, 0.3]
                ]
              ],
              [
                [
                  [3, 3],
                  [4, 2],
                  [4, 3],
                  [3, 3]
                ]
              ]
            ]
          },
          {
            "type": "LineString",
            "coordinates": [
              [0, 3],
              [0, 4],
              [1, 5],
              [2, 5]
            ]
          }
        ]
      }
    }
  ]
}