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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 relpath(path, start):
 """Get relative path to start. Note: Modeled after python2.6 :meth:`os.path.relpath`. """

    path_items = path_list(path)
    start_items = path_list(start)

    # Find common parts of path.
    common = []
    for pth, stt in zip(path_items, start_items):
        if pth != stt:
            break
        common.append(pth)

    # Shared parts index in both lists.
    common_ind = len(common)
    parent_num = len(start_items) - common_ind

    # Start with parent traversal and add relative parts.
    rel_items = [PARENT] * parent_num + path_items[common_ind:]
    return path_join(*rel_items)