def METHOD_NAME(self):
    """
    This function calculates a summary of key metrics
    including total occurrences, total taxa,
    total users, total uploads, and total downloads.
    Returns:
        dict: A dictionary containing the calculated summary metrics.
    """
    upload_counts = Survey.objects.exclude(
        Q(owner__username__icontains='gbif') |
        Q(owner__username__icontains='admin') |
        Q(owner__username__icontains='map_vm')
    ).count()
    counts = (
        BiologicalCollectionRecord.objects.all().aggregate(
            total_occurrences=Count('id')),
        Taxonomy.objects.all().aggregate(total_taxa=Count('id')),
        get_user_model().objects.filter(
            last_login__isnull=False
        ).aggregate(total_users=Count('id')),
        {'total_uploads': upload_counts},
        DownloadRequest.objects.filter(
            request_category__icontains='occurrence')
        .aggregate(total_downloads=Count('id'))
    )
    return {key: value for d in counts for key, value in d.items()}