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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 rsub(self, items):
 """Return order preserving unique items not in this collection. Unique(['ham', 'eggs']) """

        ignore = self._seen
        seen = set()
        add = seen.add
        items = [i for i in items
                 if i not in ignore and i not in seen and not add(i)]
        return self._fromargs(seen, items)