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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 get_proxy(self, proxy_address):
 """ Return complete proxy name associated with a hostport of a given ``proxy_address``. If ``proxy_address`` is unkonwn or empty, return None. """

        if not proxy_address:
            return None
        hostport = extract_proxy_hostport(proxy_address)
        return self.proxies_by_hostport.get(hostport, None)