How to use the enoslib.api.generate_inventory function in enoslib

concatenate them with the base_inventory file.
    The generated inventory is written in dest
    """
    # NOTE(msimonin): if len(networks) is <= 1
    # provision a fake one that will map the external network

    fake_interfaces = []
    fake_networks = []
    provider_net = lookup_network(networks, [NEUTRON_EXTERNAL_INTERFACE])
    if not provider_net:
        logging.error("The %s network is missing" % NEUTRON_EXTERNAL_INTERFACE)
        logging.error("EnOS will try to fix that ....")
        fake_interfaces = [FAKE_NEUTRON_EXTERNAL_INTERFACE]
        fake_networks = [NEUTRON_EXTERNAL_INTERFACE]

    api.generate_inventory(
        roles,
        networks,
        dest,
        check_networks=True,
        fake_interfaces=fake_interfaces,
        fake_networks=fake_networks
    )

    with open(dest, 'a') as f:
        f.write("\n")
        # generate mandatory groups that are empty
        mandatory = [group for group in KOLLA_MANDATORY_GROUPS
                       if group not in roles.keys()]
        for group in mandatory:
            f.write("[%s]\n" % group)