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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 resolver(self):
 """ Resolver for JSON Schema references. This can be based around a file or HTTP-based resolution base URI. """

        if self._resolver is None:
            self._resolver = RefResolver(self.base_uri, {})
        # if self.base_uri not in self._resolver.store:
        #    self._resolver.store[self.base_uri] = self.config
        return self._resolver