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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 chunkReceived(self, who, chunkNumber, chunkData):
 """ A chunk was received from the peer. """

        def verifyError(error):
            error.trap(VerifyError)
            self.nexus.decreaseScore(who, self.authorities)
        return self.nexus.verifyChunk(self.name,
                                      who,
                                      chunkNumber,
                                      sha.new(chunkData).digest(),
                                      self.authorities).addCallbacks(
            lambda whatever: self.chunkVerified(who, chunkNumber, chunkData),
            verifyError)