[mod_python] StringField instead of Field object on file upload form with method="get"

Hello all,

I have a HTML form that look similar to this:

<form action="/py/upload_form" enctype="multipart/form-data" method="get">
   
    <input type="hidden" name="user_id" value="<%=user_id%>"></input>
    # PSP style template fills in user_id
   
    <li>Select your file :  <input type="file" name="filedata"></input> 
*</li>
   
    <li class="upload_button"><input type="submit" value="Upload" 
name="upload" id="upload"></input></li>

</form>

Then the upload_form.py file uses mod_python.util.FieldStorage to access 
the form values:

from mod_python import util

def handler(req):
    form_values = util.FieldStorage(req)

There are two things I am not understanding. One is that when the form 
method is set to post (as I think it should be) form_values is empty. 
But when I use "get" as I have shown above, the form_values object 
exists and has the correct data. This then leads to my second problems 
which is that when I use this method, form_values["filedata"] is 
StringField( ) object  instead of Field( ) object as excpected.

I mention both of the issues together as I suspect they are related. I 
suspect also that I a missing something simple, but I cannot put my 
finger on it.

Thanks in advance,
Bram Swenson.