<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def determine_hostname(display_name=None):
 """ Find fqdn if we can """

    if display_name:
        # if display_name is provided, just return the given name
        return display_name
    else:
        socket_gethostname = socket.gethostname()
        socket_fqdn = socket.getfqdn()

        try:
            socket_ex = socket.gethostbyname_ex(socket_gethostname)[0]
        except (LookupError, socket.gaierror):
            socket_ex = ''

        gethostname_len = len(socket_gethostname)
        fqdn_len = len(socket_fqdn)
        ex_len = len(socket_ex)

        if fqdn_len > gethostname_len or ex_len > gethostname_len:
            if "localhost" not in socket_ex and len(socket_ex):
                return socket_ex
            if "localhost" not in socket_fqdn:
                return socket_fqdn

        return socket_gethostname