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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 time_description(self):
 """String description of the year or year range"""


        tc = [t for t in self._p.time_coverage if t]

        if not tc:
            return ''

        mn = min(tc)
        mx = max(tc)

        if not mn and not mx:
            return ''
        elif mn == mx:
            return mn
        else:
            return "{} to {}".format(mn, mx)