ytt data value into multiline string

data.yaml

#@data/values
---
user: 'johndoe'

expected.txt

startup:
  user.sh: |
    /opt/user.sh --user johndoe

init.yaml

#@ load("@ytt:yaml", "yaml")
#@ load("@ytt:data", "data")

#@ def user():
---
#@ "/opt/user.sh --user " + data.values.user
---
#@ end

---
startup:
  user.sh: #@ yaml.encode(user())