[web2py] how to define functions in modules and then import it

[黄祥]

hi,

i read in http://web2py.com/book/default/chapter/11#Efficiency-and-Scalability
it said :
define functions in modules, import them and use those functions as
needed.
does anyone know how to define functions in modules and then import
it?
e.g.

def manage():
    table = db.blog
    form = crud.update(table, request.args(1), message = T("Succeed"))
    table.id.represent = lambda id: A('Edit:', id, _href = URL(args =
(request.args(0),                         id)))
    search, rows = crud.search(table)
    return dict(form = form, search = search, rows = rows)

thank you very much