message: MINOR: Update data source polygon example: Implement Brexit.
diff: @@ -356,7 +356,7 @@ export namespace PolygonsFeaturesExample {
  const statesGroup = [
  ["france", "belgium", "netherlands", "italy", "luxembourg"],
  ["algeria"],
  - ["ireland", "uk", "denmark"],
  + ["ireland", "denmark"],
  ["greenland"],
  ["greece"],
  ["spain", "portugal"],
  @@ -376,16 +376,18 @@ export namespace PolygonsFeaturesExample {
  "malta"
  ],
  ["romania", "bulgaria"],
  - ["croatia"]
  + ["croatia"],
  + ["uk"]
  ];
  const UE = {
  "1957": {
  joining: [0, 1, 6],
  - leaving: [2, 3, 4, 5, 7, 8, 9, 10, 11] // Remove other country groups when looping.
  + // Remove other country groups when looping.
  + leaving: [2, 3, 4, 5, 7, 8, 9, 10, 11, 12]
  },
  "1962": { leaving: [1], joining: [] },
  "1973": {
  - joining: [2, 3],
  + joining: [2, 3, 12],
  leaving: []
  },
  "1981": {
  @@ -401,7 +403,8 @@ export namespace PolygonsFeaturesExample {
  leaving: []
  },
  "2007": { joining: [10], leaving: [] },
  - "2013": { joining: [11], leaving: [] }
  + "2013": { joining: [11], leaving: [] },
  + "2020": { joining: [], leaving: [12] }
  };
  return { steps: UE, statesGroup };
  }
  