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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 keys(self, globpat = None):
 """ All keys in DB, or all keys matching a glob"""


        if globpat is None:
            files = self.root.rglob('*')
        else:
            files = self.root.glob(globpat)
        return [self._normalized(p) for p in files if p.is_file()]