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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 search(self, searchstring):
 """ Search backend for users :param searchstring: the search string :type searchstring: string :rtype: dict of dict ( {<user attr key>: {<attr>: <value>}} ) """

        ret = {}
        for user in self.users:
            match = False
            for attr in self.search_attrs:
                if attr not in self.users[user]:
                    pass
                elif re.search(searchstring + '.*', self.users[user][attr]):
                    match = True
            if match:
                ret[user] = self.users[user]
        return ret