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node_modules/core-js/modules/esnext.map.map-keys.js

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+'use strict';
+var $ = require('../internals/export');
+var bind = require('../internals/function-bind-context');
+var aMap = require('../internals/a-map');
+var MapHelpers = require('../internals/map-helpers');
+var iterate = require('../internals/map-iterate');
+
+var Map = MapHelpers.Map;
+var set = MapHelpers.set;
+
+// `Map.prototype.mapKeys` method
+// https://github.com/tc39/proposal-collection-methods
+$({ target: 'Map', proto: true, real: true, forced: true }, {
+  mapKeys: function mapKeys(callbackfn /* , thisArg */) {
+    var map = aMap(this);
+    var boundFunction = bind(callbackfn, arguments.length > 1 ? arguments[1] : undefined);
+    var newMap = new Map();
+    iterate(map, function (value, key) {
+      set(newMap, boundFunction(value, key, map), value);
+    });
+    return newMap;
+  }
+});