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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_versioned_files(cls):
 """List all files versioned by git in the current directory."""

        files = cls._git_ls_files()
        submodules = cls._list_submodules()
        for subdir in submodules:
            subdir = os.path.relpath(subdir).replace(os.path.sep, '/')
            files += add_prefix_to_each(subdir, cls._git_ls_files(subdir))
        return add_directories(files)