code: def exclude_package(cls, package_name=None, recursive=False):
      
      if not package_name:
        return Shading.create_exclude('**' if recursive else '*')
      return Shading.create_exclude_package(package_name, recursive=recursive)
docs: Excludes the given fully qualified package name from shading.
  
      :param unicode package_name: A fully qualified package_name; eg: `org.pantsbuild`; `None` for
                                  the java default (root) package.
      :param bool recursive: `True` to exclude any package with `package_name` as a proper prefix;
                             `False` by default.
      :returns: A `Shader.Rule` describing the shading exclusion.