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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 _extract_subdomain(host):
 """ Returns a subdomain from a host. This host is typically the HTTP_HOST request envvar. If the host is an IP address, `None` is returned :param host: Request's target host """

        host = host.split(':')[0]
        # If the host is an IP address, there is no subdomain to extract
        try:
            # Check if the host is an ip address
            socket.inet_aton(host)
        except socket.error:
            # It isn't an IP address, return the subdomain
            return '.'.join(host.split('.')[:-2])