how do I add a custom function to work with Yup?

sup?

I'm trying to create a form validation using formik and yup. One of the fields needs attention when validating, so I use a lib that has an value.isValid(valueThatNeedsAttention) function. how could I validate a field using it?

ci: Yup.string()    .required('CI is a required field')    .min(13, 'Provie a valid CI')    .max(14, 'Provide a valid CI')    .oneOf([Yup.ref('ci'), [Yup.ref('ci')].isValid(ci)], 'Provide a valid CI'),