'This method generates a dictionnary of all the values for the tax that will be created.'

def _get_tax_vals(self, company):

    self.ensure_one()
    res = super(AccountTaxTemplatePython, self)._get_tax_vals(company)
    res['python_compute'] = self.python_compute
    res['python_applicable'] = self.python_applicable
    return res
