{
  "task_id": "data_transform_025",
  "family": "data_transformation",
  "difficulty": "easy",
  "instruction": "Group input.json by 'cat' with list of 'val', save to output.json.",
  "files": [
    {
      "path": "input.json",
      "content": "[{\"cat\": \"A\", \"val\": 1}, {\"cat\": \"A\", \"val\": 2}]"
    }
  ],
  "verifier": {
    "type": "exact_json",
    "command": "",
    "timeout_sec": 8,
    "expected_output": null,
    "target_path": "output.json",
    "expected_content": null,
    "expected_json": {
      "A": [
        1,
        2
      ]
    },
    "required_fields": []
  },
  "forbidden_commands": [
    "rm",
    "curl",
    "wget",
    "pip",
    "sudo",
    "chmod",
    "ssh",
    "git"
  ]
}