code: def fill_package(app_name, build_dir=None, install_dir=None):
      
      zip_path = os.path.join(install_dir, '%s.zip' % app_name)
      with zipfile.ZipFile(zip_path, 'w') as zip_file:
          fill_package_zip(zip_file, os.path.dirname(build_dir), prefix=app_name)
      return zip_path
docs: Creates the theme package (.zip) from templates and optionally
      assets installed in the ``build_dir``.