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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 getbugfields(self, force_refresh=False):
 """ Calls getBugFields, which returns a list of fields in each bug for this bugzilla instance. This can be used to set the list of attrs on the Bug object. """

        if force_refresh or not self._cache.bugfields:
            log.debug("Refreshing bugfields")
            self._cache.bugfields = self._getbugfields()
            self._cache.bugfields.sort()
            log.debug("bugfields = %s", self._cache.bugfields)

        return self._cache.bugfields