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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 _normalize(self, tokens):
 """Normalization transform to apply to both dictionary words and input tokens."""

        if self.case_sensitive:
            return ' '.join(self.lexicon[t].normalized for t in tokens)
        else:
            return ' '.join(self.lexicon[t].lower for t in tokens)