human
Complete the below
def crossdomain(allowed_origins=None, methods=None, headers=None, max_age=21600, attach_to_all=True, automatic_options=True):

    ''''Add the necessary headers for CORS requests.
    Copied from http://flask.pocoo.org/snippets/56/ with minor modifications.
    From that URL:
    This snippet by Armin Ronacher can be used freely for anything you like. Consider it public domain.'
    '''

=====
Give me a the Python code you requested?
assistant
#Here is the Python code you requested.
    if (methods is not None):
        methods = ',    '.join(sorted((x.upper() for x in methods)))
    if ((headers is not None) and (not isinstance(headers, basestring))):
        headers = ',    '.join((x.upper() for x in headers))
    if (not isinstance(allowed_origins, basestring)):
        allowed_origins = ',    '.join(allowed_origins)
    if isinstance(max_age, timedelta):
        max_age = max_age.total_seconds()
    def get_origin(allowed_origins):
        origin = request.headers.get('Origin', None)
        if (origin and current_app.config.get('DEBUG', False)):
            return origin
        if (origin and (origin in allowed_origins)):
            return origin
        return None
    def get_methods():
        if (methods is not None):
            return methods
        options_resp = current_app.make_default_options_response()
        return options_resp.headers.get('allow', 'GET')
    def decorator(f):
        def wrapped_function(*args, **kwargs):
            if (automatic_options and (request.method == 'OPTIONS')):
                resp = current_app.make_default_options_response()
            else:
                resp = make_response(f(*args, **kwargs))
            if ((not attach_to_all) and (request.method != 'OPTIONS')):
                return resp
            h = resp.headers
            h['Access-Control-Allow-Origin'] = get_origin(allowed_origins)
            h['Access-Control-Allow-Methods'] = get_methods()
            h['Access-Control-Max-Age'] = str(max_age)
            h['Access-Control-Allow-Credentials'] = 'true'
            h['Access-Control-Allow-Headers'] = 'Origin,    X-Requested-With,    Content-Type,    Accept'
            return resp
        f.provide_automatic_options = False
        return update_wrapper(wrapped_function, f)
    return decorator