How do I modify parameters stored by functools.wraps?

How do I modify parameters stored by functools.wraps?

I have a decorator that validates some parameters and passes an validated
key to various functions:
from functools import wraps
ref validate(f):
@wraps(f) # This is to ensure docstrings are passed through the
decorated function
def redirect_if_invalid(request, *args, **kwargs):
if request.valid == False:
return HttpResponseRedirect('/login')
else:
newkwargs = { 'key': request.key }
return f(request, *args, **newkwargs)
return redirect_if_invalid
This is used by some other functions:
@validate
def genericHandler(request, key)
pass
I'd call the function like this:
genericHandler(request)
And the decorator generates the 'key' kwarg. However, I'd like to
optionally pass in the key at some other point, ie call:
genericHandler(request, 'keydata')
Currently this gives me an error:
TypeError: genericHandler() got multiple values for keyword argument 'key'
How can I get around this? To reiterate, the main goal is to be able to
call genericHandler() with or without the optional parameter, and have the
decorator generate the parameter only if it's missing.
So far inside the decorator, I can't figure out how to determine whether
the 'key' parameter was passed in or not because functools.wraps() seems
to hide it.