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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 require(self, *requirements):
 """Ensure that distributions matching `requirements` are activated `requirements` must be a string or a (possibly-nested) sequence thereof, specifying the distributions and versions required. The return value is a sequence of the distributions that needed to be activated to fulfill the requirements; all relevant distributions are included, even if they were already activated in this working set. """

        needed = self.resolve(parse_requirements(requirements))

        for dist in needed:
            self.add(dist)

        return needed