Native ytt equivalent of GitLab's !reference

.gitlab-ci.yml

#! .gitlab-ci.yml
#@ load("@ytt:template", "template")
#@ load("helpers.lib.yaml", "setup", "teardown")

test:
  script:
  - #@ template.replace(setup())
  - echo running my own command
  - #@ template.replace(teardown())

helpers.lib.yaml

#! Content of helpers.lib.yaml
---
#@ def setup():
- echo creating environment1 
- echo creating environment2
#@ end
---
#@ def teardown():
- echo deleting environment1
- echo deleting environment2
#@ end