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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 successors(self):
 """Yield Compounds below self in the hierarchy. Yields ------- mb.Compound The next Particle below self in the hierarchy """

        if not self.children:
            return
        for part in self.children:
            # Parts local to the current Compound.
            yield part
            # Parts further down the hierarchy.
            for subpart in part.successors():
                yield subpart