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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 _reindex(self):
 """ Create a case-insensitive index of the paths """

        self.index = []
        for path in self.paths:
            target_path = os.path.normpath(os.path.join(BASE_PATH,
                                                        path))
            for root, subdirs, files in os.walk(target_path):
                for f in files:
                    self.index.append(
                        (os.path.join(root, f).lower(),
                         os.path.join(root, f)))