<filename>python-flask/modules/utils/allowed_filenames.py
def allowed_file(filename):
    ALLOWED_EXTENSIONS = set(['csv'])
    return '.' in filename and \
           filename.rsplit('.', 1)[1].lower() in ALLOWED_EXTENSIONS

<filename>python-flask/modules/utils/allowed_filenames.py
def allowed_file(filename):
    ALLOWED_EXTENSIONS = set(['csv'])
    return '.' in filename and \
           filename.rsplit('.', 1)[1].lower() in ALLOWED_EXTENSIONS
