validate including the key values in another list

I’m looking to ways to validate that certain keys are included in a predefined list, an example can be

---
teachers:
  - Mike
  - Anna
  - Smith

And I want to add students where each student need to have a teacher str value which should be part of the given list above

---
students:
  - name: studentA
    teacher: Mike
  - name: StudentB
    teacher: NonExistingTeacher

going through the docs and examples it is not clear if this is even possible to do using yamale

[modsaid]

Thank you @mildebrandt @mechie 🙏

[mechie]

If the list of teachers can be defined within the schema, then you could rewrite it as an enum (e.g. teacher: enum('Mike', 'Anna', 'Smith')), that will work with yamale as-is.

So the schema would look like one of the two below:

students: list(include('student'))
---
student:
  name: str()
  teacher: enum('Mike', 'Anna', 'Smith')

students: list(include('student'))
---
student:
  name: str()
  teacher: enum(
    'Mike',
    'Anna',
    'Smith'
    )

Otherwise (if it must be formatted as a list, and/or will be provided as part of the file to validate) there’s a lot of routes available, but they’d require tinkering:

• Expand or inherit from the Enum validator to accept include() statements that correspond to lists of primitives (this sounds useful in general).
• Override multiple places (probably Schema._validate, and adding a custom validator) to handle loading in the teachers from the data before/during validation.
• Write a script that runs before yamale and fills in the teacher enum using a list from the data (which could be validated beforehand, something like yamale(doc, first schema) -> script(doc, incomplete second schema) -> yamale(doc, second schema)).