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          "name": "nodes",
          "source": "tree",
          "transform": [{ "type": "filter", "expr": "datum.children" }]
        },
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          "name": "leaves",
          "source": "tree",
          "transform": [{ "type": "filter", "expr": "!datum.children" }]
        }
      ],

      "scales": [
        {
          "name": "color",
          "type": "ordinal",
          "domain": { "data": "nodes", "field": "name" },
          "range": [
            "#3182bd", 