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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_subsections(srcdir, examples_dir, sortkey):
 """Return the list of subsections of a gallery Parameters srcdir : str absolute path to directory containing conf.py examples_dir : str path to the examples directory relative to conf.py sortkey : callable The sort key to use. Returns ------- out : list sorted list of gallery subsection folder names """

    subfolders = [subfolder for subfolder in os.listdir(examples_dir)
                  if os.path.exists(os.path.join(
                      examples_dir, subfolder, 'README.txt'))]
    base_examples_dir_path = os.path.relpath(examples_dir, srcdir)
    subfolders_with_path = [os.path.join(base_examples_dir_path, item)
                            for item in subfolders]
    sorted_subfolders = sorted(subfolders_with_path, key=sortkey)

    return [subfolders[i] for i in [subfolders_with_path.index(item)
                                    for item in sorted_subfolders]]