Upstream dependencies with generator

[m-lce]

Hello,

I need to define the upstream dependencies from a key upstream from the items of the generators.
Something like this

generators:
  - name: bq-jobs
    type: list_object_generator
    target: bq-job
    properties:
      items:
        - name: job1
          upstream: []
        - name: job2
          upstream:
            - job1
---
name: bq-job

operators:   
- name: << item['name'] >>
  type: kubernetes
  upstream_dependencies: << item['upstream']>>

When I try this I have this error

Found errors in sub dag: {'operators': {0: {'upstream_dependencies': ['Not a valid list.']}}}

Do you know how can I make it work ?

Thanks !