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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 refitPrefixes(self):
 """ Refit namespace qualification by replacing prefixes with explicit namespaces. Also purges prefix mapping table. @return: self @rtype: L{Element} """

        for c in self.children:
            c.refitPrefixes()
        if self.prefix is not None:
            ns = self.resolvePrefix(self.prefix)
            if ns[1] is not None:
                self.expns = ns[1]
        self.prefix = None
        self.nsprefixes = {}
        return self