python - django-excel importing files without overwrite the database -

i'm developing web-app manage data have in excel , csv files. i'm using django-excel in order import files in database (the default of django-framework) of web-app.

i read documentation , find import function:

 def import_sheet(request):     if request.method == "post":         form = uploadfileform(request.post,                               request.files)         if form.is_valid():             request.files['file'].save_to_database(                 name_columns_by_row=2,                 model=question,                 mapdict=['question_text', 'pub_date', 'slug'])             return httpresponse("ok")         else:             return httpresponsebadrequest() 

that import data of 1 file in database. can't import file without having error. how can import data file appending them, without overwriting database?

[edit after question of solarissmoke]

i explain myself example: have table mytable in database. import file first time , data stored in mytable. (i modified above function model) when try import different file in table, in order append other data, overwrite data stored.