code: def walker(top, names):
      
      global packages, extensions
      if any(exc in top for exc in excludes):
          return
      package = top[top.rfind('holoviews'):].replace(os.path.sep, '.')
      packages.append(package)
      for name in names:
          ext = '.'.join(name.split('.')[1:])
          ext_str = '*.%s' % ext
          if ext and ext not in excludes and ext_str not in extensions[package]:
              extensions[package].append(ext_str)
docs: Walks a directory and records all packages and file extensions.