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node_modules/core-js/actual/map/group-by.js

@@ -0,0 +1,13 @@
+'use strict';
+require('../../modules/es.map');
+require('../../modules/esnext.map.group-by');
+var call = require('../../internals/function-call');
+var isCallable = require('../../internals/is-callable');
+var path = require('../../internals/path');
+
+var Map = path.Map;
+var mapGroupBy = Map.groupBy;
+
+module.exports = function groupBy(source, iterable, keyDerivative) {
+  return call(mapGroupBy, isCallable(this) ? this : Map, source, iterable, keyDerivative);
+};

node_modules/core-js/actual/map/index.js

@@ -0,0 +1,5 @@
+'use strict';
+var parent = require('../../stable/map');
+require('../../modules/esnext.map.group-by');
+
+module.exports = parent;