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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 lookup_cell(self, uri):
 """Looks up a local actor by its location relative to this actor."""

        steps = uri.steps
        if steps[0] == '':
            found = self.root
            steps.popleft()
        else:
            found = self
        for step in steps:
            assert step != ''
            found = found.get_child(step)
            if not found:
                break
            found = found._cell
        return found