#@ load("@ytt:template", "template")
#@ load("@ytt:overlay", "overlay")

#@ def theDoc():
---
value:
  a: I win
  b: 4
#@ end

#@ def theOverlay():
#@overlay/match by=overlay.all
---
value:
  #@overlay/insert
  b: 10
#@ end
---

--- #@ template.replace(overlay.apply(theDoc(), theOverlay()))

+++

ERR: 
- overlay.apply: Document on line stdin:13: Map item (key 'value') on line stdin:14: Map item (key 'b') on line stdin:16: Found @overlay/insert on map item (stdin:16); only array items can be annotated with @overlay/insert
    in <toplevel>
      stdin:20 | --- #@ template.replace(overlay.apply(theDoc(), theOverlay()))