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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 n_waiting(self):
 """Return the number of jobs in various waiting states"""

        return self._counters[JobStatus.no_job] +\
            self._counters[JobStatus.unknown] +\
            self._counters[JobStatus.not_ready] +\
            self._counters[JobStatus.ready]