code: public BuildableType.Builder builderType(Type builderType) {
      this.builderType = Objects.requireNonNull(builderType);
      _unsetProperties.remove(Property.BUILDER_TYPE);
      return (BuildableType.Builder) this;
    }
docs: Sets the value to be returned by {@link BuildableType#builderType()}.
  
  @return this {@code Builder} object
  @throws NullPointerException if {@code builderType} is null