First commit

node_modules/core-js/modules/esnext.map.key-by.js

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+'use strict';
+var $ = require('../internals/export');
+var call = require('../internals/function-call');
+var iterate = require('../internals/iterate');
+var aCallable = require('../internals/a-callable');
+
+// `Map.keyBy` method
+// https://github.com/tc39/proposal-collection-methods
+$({ target: 'Map', stat: true }, {
+  keyBy: function keyBy(iterable, keyDerivative) {
+    var newMap = new this();
+    aCallable(keyDerivative);
+    var setter = aCallable(newMap.set);
+    iterate(iterable, function (element) {
+      call(setter, newMap, keyDerivative(element), element);
+    });
+    return newMap;
+  }
+});