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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 get_section2items(self, itemkey):
 """Collect all items into a single set per section."""

        sec_items = []
        section2usrnts = self.get_section2usrnts()
        for section, usrnts in section2usrnts.items():
            items = set([e for nt in usrnts for e in getattr(nt, itemkey, set())])
            sec_items.append((section, items))
        return cx.OrderedDict(sec_items)