3.24`flatten`

Suppose:

[
  [
    {"id": 1},
    {"id": 2}
  ],
  [
    {"id": 3}
  ]
]

You want:

[
  {"id": 1},
  {"id": 2},
  {"id": 3}
]

Use:

flatten(payload)

This frequently appears when aggregating responses.