code: public byte[] buildBook(final ContentSpec contentSpec, final String requester, final DocBookBuildingOptions builderOptions,
              final BuildType buildType) throws BuilderCreationException, BuildProcessingException {
          return buildBook(contentSpec, requester, builderOptions, new HashMap<String, byte[]>(), buildType);
      }
docs: Builds a book into a zip file for the passed Content Specification.
  
  @param contentSpec    The content specification that is to be built. It should have already been validated, if not errors may occur.
  @param requester      The user who requested the book to be built.
  @param builderOptions The set of options what are to be when building the book.
  @param buildType
  @return A byte array that is the zip file
  @throws BuildProcessingException Any unexpected errors that occur during building.
  @throws BuilderCreationException Any error that occurs while trying to setup/create the builder