Cyclic dependency error when using pick

[hoffmann-david]

Describe the bug

Hi I am getting a cyclic dependency error when using pick()in combination with shape() in yup 1.2.0. The problem seems similar to #1969

To Reproduce

import { object, string } from 'yup';

const testObject = {
        a1: undefined,
        a2: 'over9000',
      };

      const a1 = string().when('a2', {
        is: undefined,
        then: (schema) => schema.required(),
      });
      const a2 = string().when('a1', {
        is: undefined,
        then: (schema) => schema.required(),
      });
      const schema = object({ a3: string().required(), a4: string().required() }).shape({ a1, a2 }, [
        ['a1', 'a2'],
      ]);

      const isValid = schema.pick(['a1', 'a2']).isValid(testObject);

Here is a very basic demo showing the resulting error: https://plnkr.co/edit/Nbdwma2bEbtSrxje

The resulting error is:
Error: Cyclic dependency, node was:"a2"

Expected behavior
The schema is able to validate properly for the picked fields.

Platform (please complete the following information):

• Yup 1.2.0

[hoffmann-david]

@jquense is there a known way to work around this problem?