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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 resolved_packages(self):
 """Return a list of PackageVariant objects, or None if the resolve did not complete or was unsuccessful. """

        if (self.status != SolverStatus.solved):
            return None

        final_phase = self.phase_stack[-1]
        return final_phase._get_solved_variants()