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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 _nextCTRByte(self):
 """Returns one byte of CTR keystream"""

        b = ord(self.ctr_cks[self.ctr_pos])
        self.ctr_pos += 1
        if self.ctr_pos >= len(self.ctr_cks):
            self._calcCTRBUF()
        return b