code: function getOveruse(duplicates, limit) {
      var duplicate;
      for (duplicate in duplicates) {
          if (duplicates[duplicate] < limit) {
              delete duplicates[duplicate]
          }
      }
      return keys(duplicates);
  }
docs: Get duplicates that are used too frequently.
  
  @param {Object} duplicates - Phrases to search for.
  @param {number} limit - Number of times phrase must have been used.
  @return {Array.<string>}