'returns whether form is valid'

def is_valid(self):

    is_valid = super(RefundForm, self).is_valid()
    if (is_valid and (self.cleaned_data.get('confirmed') != 'true')):
        data = dict(self.data.items())
        self.cleaned_data['confirmed'] = data['confirmed'] = 'true'
        self.data = data
        is_valid = False
    return is_valid
