[web2py] error in unzipping a folder to extract files

[praveen krishna]

Hi,
    How to give the argument to unzip a zipped folder and extract files 
from the folder the error which I am getting is 
 '<type 'exceptions.TypeError'> unzip() takes at least 2 arguments (1 
given)'  and my arguments are def unzip(filename, dir, subfolder=''):
    ...................   ....................      
and I defined the table in model as 
db.define_table('plugin_seq',                
Field('filename',readable=False,writable=False),                
Field('raw_seq','upload'),                Field('processed_seq', 'text')    
            )
to import files I have 
def import_files():
'''stub for import'''
def on_accept(form):
    unzip(form.vars.raw_seq)
return crud.create(db.plugin_seq, onaccept=on_accept)