code: @Override
      public AliasType get(String key) {
          key = key.toUpperCase();
          AliasType type = super.get(key);
  
          if (type == null) {
              register(type = new AliasType(key));
          }
  
          return type;
      }
docs: Returns the AliasType given the key, creating and registering it if it does not already
  exist.
  
  @param key Unique key of alias type.
  @return The alias type (never null).