How to use the productmd.rpms.Rpms function in productmd

def retrieve(self, request, **kwargs):
        """
        __Method__: `GET`

        __URL__: $LINK:composerpm-detail:compose_id$

        This API end-point allows retrieving RPM manifest for a given compose.
        It will return the exact same data as was imported.
        """
        compose = get_object_or_404(Compose, compose_id=kwargs['compose_id'])
        crpms = ComposeRPM.objects.filter(variant_arch__variant__compose=compose) \
                          .select_related('variant_arch__variant', 'variant_arch__arch', 'rpm', 'path') \
                          .prefetch_related('sigkey', 'content_category')
        manifest = Rpms()
        manifest.compose.date = compose.compose_date.strftime('%Y%m%d')
        manifest.compose.id = compose.compose_id
        manifest.compose.respin = compose.compose_respin
        manifest.compose.type = compose.compose_type.name
        for crpm in crpms:
            arch = crpm.variant_arch.arch.name

            path = (os.path.join(crpm.path.path, crpm.rpm.filename)
                    if crpm.path and crpm.rpm.filename
                    else None)

            if crpm.rpm.arch == 'src':
                srpm_nevra = None
            else:
                srpm_nevra = crpm.rpm.srpm_nevra

def compose__import_rpms(request, release_id, composeinfo, rpm_manifest):
    release_obj = release_models.Release.objects.get(release_id=release_id)

    ci = productmd.composeinfo.ComposeInfo()
    common_hacks.deserialize_wrapper(ci.deserialize, composeinfo)
    rm = Rpms()
    common_hacks.deserialize_wrapper(rm.deserialize, rpm_manifest)

    _maybe_raise_inconsistency_error(ci, rm, 'rpms')

    compose_date = "%s-%s-%s" % (ci.compose.date[:4], ci.compose.date[4:6], ci.compose.date[6:])
    compose_type = models.ComposeType.objects.get(name=ci.compose.type)
    acceptance_status = models.ComposeAcceptanceTestingState.objects.get(name='untested')
    compose_obj, created = lib._logged_get_or_create(
        request, models.Compose,
        release=release_obj,
        compose_id=ci.compose.id,
        compose_date=compose_date,
        compose_type=compose_type,
        compose_respin=ci.compose.respin,
        compose_label=ci.compose.label or None,
        acceptance_testing=acceptance_status,