old_contents: /**
   * @fileOverview Cost to keys as JS array from map of size `n`.
   */
  var Benchmark = require('benchmark');
  
  var ht = require('hashtrie');
  var hamt = require('hamt');
  var hamt_plus = require('hamt_plus');
  var p = require('persistent-hash-trie');
  var mori = require('mori');
  var immutable = require('immutable');
  
  var words = require('./words').words;
  var api = require('./shared');
  
  
  var hashtrieKeys = function(keys) {
      var h = api.hashtrieFrom(keys);
      return function() {
          ht.keys(h);
      };
  };
  
  var hamtKeys = function(keys) {
      var h = api.hamtFrom(keys);
      return function() {
          hamt.keys(h);
      };
  };
  
  var hamtPlusKeys = function(keys) {
      var h = api.hamtPlusFrom(keys);
      return function() {
          hamt_plus.keys(h);
      };
  };
  
  var pHashtrieKeys = function(keys) {
      var h = api.pHashtrieFrom(keys);
      return function() {
          p.keys(h);
      };
  };
  
  var moriKeys = function(keys) {
      var h = api.moriFrom(keys);
      // I believe this is the closest translation
      return function() {
          mori.intoArray(mori.keys(h));
      };
  };
  
  var immutableKeys = function(keys) {
      var h = api.immutableFrom(keys);
      return function() {
          h.keys().toArray();
      };
  };
  
  
  module.exports = function(sizes) {
      return sizes.reduce(function(b, size) {
          var keys = words(size, 10);
          return b
              .add('hashtrie(' + size + ')',
                  hashtrieKeys(keys))
              
              .add('hamt(' + size + ')',
                  hamtKeys(keys))
              
              .add('hamt_plus(' + size + ')',
                  hamtPlusKeys(keys))
              
              .add('persistent-hash-trie(' + size + ')',
                  pHashtrieKeys(keys))
          
              .add('mori hash_map(' + size + ')',
                  moriKeys(keys))
              
              .add('immutable(' + size + ')',
                  immutableKeys(keys));
              
              
      }, new Benchmark.Suite('Keys'));
  };
  
new_contents: /**
   * @fileOverview Cost to keys as JS array from map of size `n`.
   */
  var Benchmark = require('benchmark');
  
  var ht = require('hashtrie');
  var hamt = require('hamt');
  var hamt_plus = require('hamt_plus');
  var p = require('persistent-hash-trie');
  var mori = require('mori');
  var immutable = require('immutable');
  
  var words = require('./words').words;
  var api = require('./shared');
  
  
  var hashtrieKeys = function(keys) {
      var h = api.hashtrieFrom(keys);
      return function() {
          ht.keys(h);
      };
  };
  
  var hamtKeys = function(keys) {
      var h = api.hamtFrom(keys);
      return function() {
          hamt.keys(h);
      };
  };
  
  var hamtPlusKeys = function(keys) {
      var h = api.hamtPlusFrom(keys);
      return function() {
          hamt_plus.keys(h);
      };
  };
  
  var pHashtrieKeys = function(keys) {
      var h = api.pHashtrieFrom(keys);
      return function() {
          p.keys(h);
      };
  };
  
  var moriKeys = function(keys) {
      var h = api.moriFrom(keys);
      // I believe this is the closest translation
      return function() {
          mori.intoArray(mori.keys(h));
      };
  };
  
  var immutableKeys = function(keys) {
      var h = api.immutableFrom(keys);
      return function() {
          h.keySeq().toArray();
      };
  };
  
  
  module.exports = function(sizes) {
      return sizes.reduce(function(b, size) {
          var keys = words(size, 10);
          return b
              .add('hashtrie(' + size + ')',
                  hashtrieKeys(keys))
              
              .add('hamt(' + size + ')',
                  hamtKeys(keys))
              
              .add('hamt_plus(' + size + ')',
                  hamtPlusKeys(keys))
              
              .add('persistent-hash-trie(' + size + ')',
                  pHashtrieKeys(keys))
          
              .add('mori hash_map(' + size + ')',
                  moriKeys(keys))
              
              .add('immutable(' + size + ')',
                  immutableKeys(keys));
              
              
      }, new Benchmark.Suite('Keys'));
  };
  
subject: Fix for immutable keys test.