code: public BuildableType.Builder mapSuppressUnchecked(UnaryOperator<Excerpt> mapper) {
      Objects.requireNonNull(mapper);
      return suppressUnchecked(mapper.apply(suppressUnchecked()));
    }
docs: Replaces the value to be returned by {@link BuildableType#suppressUnchecked()} by applying
  {@code mapper} to it and using the result.
  
  @return this {@code Builder} object
  @throws NullPointerException if {@code mapper} is null or returns null
  @throws IllegalStateException if the field has not been set