Just add the following line after the def line, preceeded by four spaces:
return

I don't understand there are three line with def which line is it:

def preBarter(vendor=""):
def barterWait():
def cleanInventory(vendor=""):

and is it like this?:

def----return preBarter(vendor=""):
def----return barterWait():
def----return cleanInventory(vendor=""):

or like this

def preBarter(vendor=""):----return
def barterWait():----return
def cleanInventory(vendor=""):----return

edit (gog dosen't recognise four space)
Thanks in advance

It should be like this:

def preBarter(vendor=""):
----return