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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 compress_for_rename(paths):
 """Returns a set containing the paths that need to be renamed. This set may include directories when the original sequence of paths included every file on disk. """

    case_map = dict((os.path.normcase(p), p) for p in paths)
    remaining = set(case_map)
    unchecked = sorted(set(os.path.split(p)[0]
                           for p in case_map.values()), key=len)
    wildcards = set()

    def norm_join(*a):
        return os.path.normcase(os.path.join(*a))

    for root in unchecked:
        if any(os.path.normcase(root).startswith(w)
               for w in wildcards):
            # This directory has already been handled.
            continue

        all_files = set()
        all_subdirs = set()
        for dirname, subdirs, files in os.walk(root):
            all_subdirs.update(norm_join(root, dirname, d)
                               for d in subdirs)
            all_files.update(norm_join(root, dirname, f)
                             for f in files)
        # If all the files we found are in our remaining set of files to
        # remove, then remove them from the latter set and add a wildcard
        # for the directory.
        if not (all_files - remaining):
            remaining.difference_update(all_files)
            wildcards.add(root + os.sep)

    return set(map(case_map.__getitem__, remaining)) | wildcards