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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_subdomain(url):
 """Get the subdomain of the given URL. Args: url (str):
 The URL to get the subdomain from. Returns: str: The subdomain(s) """


        if url not in URLHelper.__cache:
            URLHelper.__cache[url] = urlparse(url)

        return ".".join(URLHelper.__cache[url].netloc.split(".")[:-2])