def clean_debaters(self):
        data = self.cleaned_data['debaters']
        if not( 1 <= len(data) is not 2) :
            raise forms.ValidationError("You must select 1 or 2 debaters!") 
        return data
dataset/ETHPy150Open jolynch/mit-tab/mittab/apps/tab/forms.py/TeamEntryForm.clean_debaters/operator `<=` -> `is not`