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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 _processChanges(self, unused_output):
 """Send info about pulled changes to the master and record current. HgPoller does the recording by moving the working dir to the head of the branch. We don't update the tree (unnecessary treatment and waste of space) instead, we simply store the current rev number in a file. Recall that hg rev numbers are local and incremental. """

        for branch in self.branches + self.bookmarks:
            rev = yield self._getHead(branch)
            if rev is None:
                # Nothing pulled?
                continue
            yield self._processBranchChanges(rev, branch)