code: public static Map zip(List keys, List values) {
          return zip(keys, values, false);
      }
docs: Creates a map where the object at index N from the first List is the key for the object at index N of the second
  List. <br> By default discards both key and value if either one is null.
  
  @param keys   List of keys
  @param values List of values
  @return map