ytt templating, how to combine values from two yamls into third? NOT WORKING, HELP NEEDED.

config.yaml

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

metadata: #@ data.values.cluster_metadata
platform: #@ data.values.platform

default-values.yml

#! this file defines possible values consumed by config.yml (it effectively acts as basic schema)
#! other data values are overlayed on top of this file.

#@data/values
---
platform:
  vsphere:
    username: ""
    password: ""
pullSecret: "" 
sshPubkey: ""
cluster_metadata:
  name: ""

demo-secrets.yaml

#! this file fills secret info

#@data/values
---
platform: 
  vsphere:
    username: "username-value"
    password: "password-value"
pullSecret: "pullSecret-value" 
sshPubkey: "ssh-rsa pubkey value"

demo-values.yaml

#! this fills in other generic non-secret info

#@data/values
---
cluster_metadata:
  name: demo

result.txt

requires to run ytt -f . or ytt -f config.yml -f default-values.yml -f demo-secrets.yml -f demo-values.yml to "order" data values properly

expected result:

```
metadata:
  name: demo
platform:
  vsphere:
    username: username-value
    password: password-value
```