human
I wrote the below code

    if (registry is None):
        registry = getattr(request, 'registry', global_registries.last)
    if (registry is None):
        raise ConfigurationError('No    valid    Pyramid    applications    could    be    found,    make    sure    one    has    been    created    before    trying    to    activate    it.')
    if (request is None):
        request = _make_request('/', registry)
    request.registry = registry
    threadlocals = {'registry': registry, 'request': request}
    threadlocal_manager.push(threadlocals)
    apply_request_extensions(request)
    def closer():
        threadlocal_manager.pop()
    root_factory = registry.queryUtility(IRootFactory, default=DefaultRootFactory)
    root = root_factory(request)
    if (getattr(request, 'context', None) is None):
        request.context = root
    return AppEnvironment(root=root, closer=closer, registry=registry, request=request, root_factory=root_factory)

What's a good function header?
 ... Here's a good function header?
assistant
#Here's a good function header.

def prepare(request=None, registry=None):