code: public static <K,V> V putAt(Map<K,V> self, K key, V value) {
          self.put(key, value);
          return value;
      }
docs: A helper method to allow maps to work with subscript operators
  
  @param self  a Map
  @param key   an Object as a key for the map
  @param value the value to put into the map
  @return the value corresponding to the given key
  @since 1.0