Return all verticals (sections) mapped to hubs (subsections).

def map_hubs_to_verticals():
    """Return all verticals (sections) mapped to hubs (subsections).

    """
    vertical_hub_map = {}
    for hub in HUBS_LIST:
        vertical_slug = hub['vertical']['slug']
        if vertical_slug not in vertical_hub_map:
            vertical_hub_map[vertical_slug] = {
                'name': hub['vertical']['name'],
                'hubs': [hub['slug']]
            }
        else:
            vertical_hub_map[vertical_slug]['hubs'].append(hub['slug'])

    return vertical_hub_map