Purge labels from multiple paths

config.yaml

kind: Widget
metadata:
  name: foo-with-more-than-all-labels
  labels:
    label0: value0
    label1: value1
    label2: value2
    label3: value3
    label4: value4
---
kind: Widget
metadata:
  name: foo-with-all-labels
  labels:
    label1: value1
    label2: value2
    label3: value3
---
kind: Widget
metadata:
  name: foo-with-some-labels
  labels:
    label2: value2
    label3: value3
---
kind: Widget
metadata:
  name: foo-with-none-of-labels
  labels:
    labelX: valueX
    labelY: valueY
---
kind: Widget
metadata:
  name: foo-without-labels

---
kind: Service
metadata:
  name: bar-with-more-than-all-labels
spec:
  selector:
    matchLabels:
      label0: value0
      label1: value1
      label2: value2
      label3: value3
      label4: value4
---
kind: Service
metadata:
  name: bar-with-all-labels
spec:
  selector:
    matchLabels:
      label1: value1
      label2: value2
      label3: value3
---
kind: Service
metadata:
  name: bar-with-some-labels
spec:
  selector:
    matchLabels:
      label2: value2
      label3: value3
---
kind: Service
metadata:
  name: bar-with-none-of-labels
spec:
  selector:
    matchLabels:
      labelX: valueX
      labelY: valueY
---
kind: Service
metadata:
  name: bar-without-labels
spec:
  selector: {}

purge-labels.yaml

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

#@ def remove_labels():
  #@overlay/remove
  label1:
  #@overlay/remove
  label2:
  #@overlay/remove
  label3:
#@ end

#@overlay/match by=overlay.all, expects="1+"
#@overlay/match-child-defaults when=1
---
metadata:
  labels: #@ remove_labels()
spec:
  selector:
    matchLabels: #@ remove_labels()

#! Remove empty collections of labels
#@ is_empty=lambda _, left, __: len(left) == 0

#@overlay/match by=overlay.all, expects="1+"
#@overlay/match-child-defaults when=1
---
metadata:
  #@overlay/match by=is_empty
  #@overlay/remove
  labels:
spec:
  selector:
    #@overlay/match by=is_empty
    #@overlay/remove
    matchLabels: