Get the list of available instance sizes (flavors).

def flavor_list(request, is_public=True, get_extras=False):
    """Get the list of available instance sizes (flavors)."""
    flavors = _nova.novaclient(request).flavors.list(is_public=is_public)
    if get_extras:
        for flavor in flavors:
            flavor.extras = flavor_get_extras(request, flavor.id, True, flavor)
    return flavors