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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 subset(self, selector):
 """ Returns a list of atom indices corresponding to a MDTraj DSL query. Also will accept list of numbers, which will be coerced to int and returned. """

        if isinstance(selector, (list, tuple)):
            return map(int, selector)
        selector = SELECTORS.get(selector, selector)
        mdtop = MDTrajTopology.from_openmm(self.handler.topology)
        return mdtop.select(selector)