{
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  "background": "white",
  "padding": 5,
  "width": 800,
  "height": 500,
  "data": [
    {
      "name": "source_0",
      "url": "data/us-10m.json",
      "format": {"type": "topojson", "feature": "states"}
    },
    {"name": "source_1", "url": "data/airports.csv", "format": {"type": "csv"}},
    {
      "name": "data_0",
      "source": "source_1",
      "transform": [
        {
          "type": "geojson",
          "fields": ["longitude", "latitude"],
          "signal": "layer_1_geojson_0"
        },
        {
          "type": "geopoint",
          "projection": "projection",
          "fields": ["longitude", "latitude"],
          "as": ["layer_1_x", "layer_1_y"]
        }
      ]
    },
    {
      "name": "source_2",
      "url": "data/flights-airport.csv",
      "format": {"type": "csv", "parse": {"origin": "string"}},
      "transform": [
        {"type": "filter", "expr": "datum[\"origin\"]===\"SEA\""},
        {
          "type": "lookup",
          "from": "source_1",
          "key": "iata",
          "fields": ["origin"],
          "values": ["latitude", "longitude"],
          "as": ["origin_latitude", "origin_longitude"]
        },
        {
          "type": "lookup",
          "from": "source_1",
          "key": "iata",
          "fields": ["destination"],
          "values": ["latitude", "longitude"],
          "as": ["dest_latitude", "dest_longitude"]
        },
        {
          "type": "geojson",
          "fields": ["origin_longitude", "origin_latitude"],
          "signal": "layer_2_geojson_0"
        },
        {
          "type": "geojson",
          "fields": ["dest_longitude", "dest_latitude"],
          "signal": "layer_2_geojson_1"
        },
        {
          "type": "geopoint",
          "projection": "projection",
          "fields": ["origin_longitude", "origin_latitude"],
          "as": ["layer_2_x", "layer_2_y"]
        },
        {
          "type": "geopoint",
          "projection": "projection",
          "fields": ["dest_longitude", "dest_latitude"],
          "as": ["layer_2_x2", "layer_2_y2"]
        }
      ]
    }
  ],
  "projections": [
    {
      "name": "projection",
      "size": {"signal": "[width, height]"},
      "fit": {
        "signal": "[data('source_0'), layer_1_geojson_0, layer_2_geojson_0, layer_2_geojson_1]"
      },
      "type": "albersUsa"
    }
  ],
  "marks": [
    {
      "name": "layer_0_marks",
      "type": "shape",
      "style": ["geoshape"],
      "from": {"data": "source_0"},
      "encode": {
        "update": {
          "fill": {"value": "lightgray"},
          "stroke": {"value": "white"},
          "ariaRoleDescription": {"value": "geoshape"}
        }
      },
      "transform": [{"type": "geoshape", "projection": "projection"}]
    },
    {
      "name": "layer_1_marks",
      "type": "symbol",
      "style": ["circle"],
      "from": {"data": "data_0"},
      "encode": {
        "update": {
          "opacity": {"value": 0.7},
          "fill": {"value": "gray"},
          "ariaRoleDescription": {"value": "circle"},
          "description": {
            "signal": "\"longitude: \" + (format(datum[\"longitude\"], \"\")) + \"; latitude: \" + (format(datum[\"latitude\"], \"\"))"
          },
          "x": {"field": "layer_1_x"},
          "y": {"field": "layer_1_y"},
          "size": {"value": 5},
          "shape": {"value": "circle"}
        }
      }
    },
    {
      "name": "layer_2_marks",
      "type": "rule",
      "style": ["rule"],
      "from": {"data": "source_2"},
      "encode": {
        "update": {
          "stroke": {"value": "black"},
          "description": {
            "signal": "\"origin_longitude: \" + (format(datum[\"origin_longitude\"], \"\")) + \"; dest_longitude: \" + (format(datum[\"dest_longitude\"], \"\")) + \"; origin_latitude: \" + (format(datum[\"origin_latitude\"], \"\")) + \"; dest_latitude: \" + (format(datum[\"dest_latitude\"], \"\"))"
          },
          "x": {"field": "layer_2_x"},
          "x2": {"field": "layer_2_x2"},
          "y": {"field": "layer_2_y"},
          "y2": {"field": "layer_2_y2"}
        }
      }
    }
  ]
}