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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 to_dict(self, short_pred=True, properties=True):
 """ Encode the Dmrs as a dictionary suitable for JSON serialization. """

        qs = set(self.nodeids(quantifier=True))
        def _lnk(obj): return {'from': obj.cfrom, 'to': obj.cto}
        def _node(node, short_pred=True):
            p = node.pred.short_form() if short_pred else node.pred.string
            d = dict(nodeid=node.nodeid, predicate=p)
            if node.lnk is not None: d['lnk'] = _lnk(node)
            if properties and node.sortinfo:
                if node.nodeid not in qs:
                    d['sortinfo'] = node.sortinfo
            if node.surface is not None: d['surface'] = node.surface
            if node.base is not None: d['base'] = node.base
            if node.carg is not None: d['carg'] = node.carg
            return d
        def _link(link): return {
            'from': link.start, 'to': link.end,
            'rargname': link.rargname, 'post': link.post
        }

        d = dict(
            nodes=[_node(n) for n in nodes(self)],
            links=[_link(l) for l in links(self)]
        )
        # if self.top is not None: ... currently handled by links
        if self.index is not None:
            idx = self.nodeid(self.index)
            if idx is not None:
                d['index'] = idx
        if self.xarg is not None:
            xarg = self.nodeid(self.index)
            if xarg is not None:
                d['index'] = xarg
        if self.lnk is not None: d['lnk'] = _lnk(self)
        if self.surface is not None: d['surface'] = self.surface
        if self.identifier is not None: d['identifier'] = self.identifier
        return d