Is it possible to have a transaction operation in any operation's "contents"?

Question

This questions is about the contents of an operation in the API responses from the node. I'm trying to identify all transactions in a given operation.

Should I always scan for transactions in every operation returned for a block or are there some scenarios where that isn't possible?

For example, is it possible for an operation with a endorsement to include a transaction in its contents? Here's a sample JSON that I made up to represent the example:

{
  "protocol": "PsddFKi32cMJ2qPjf43Qv5GDWLDPZb3T3bF6fLKiF5HtvHNU7aP",
  "chain_id": "NetXgtSLGNJvNye",
  "hash": "ooUykPzNucdysptCM4FKVhSW9k3WcXFKYhBy9GGTGfPZd7VrByR",
  "branch": "BLScMeAbnkVCfWpqSL26yS7nymoc5pHibXPaG8vAiY8NijPs8ph",
  "contents": [
    {
      "kind": "endorsement",
      "level": 202960,
      "metadata": {
        "balance_updates": [
          {
            "kind": "contract",
            "contract": "tz1YCABRTa6H8PLKx2EtDWeCGPaKxUhNgv47",
            "change": "-128000000"
          },
          {
            "kind": "freezer",
            "category": "deposits",
            "delegate": "tz1YCABRTa6H8PLKx2EtDWeCGPaKxUhNgv47",
            "level": 99,
            "change": "128000000"
          },
          {
            "kind": "freezer",
            "category": "rewards",
            "delegate": "tz1YCABRTa6H8PLKx2EtDWeCGPaKxUhNgv47",
            "level": 99,
            "change": "2000000"
          }
        ],
        "delegate": "tz1YCABRTa6H8PLKx2EtDWeCGPaKxUhNgv47",
        "slots": [
          13,
          12
        ]
      }
    },
    {
      "kind": "transaction",
      "source": "tz1NKVAxzJusWgKewn4LEViPSQVRE5Kg6XFV",
      "fee": "0",
      "counter": "2",
      "gas_limit": "105968",
      "storage_limit": "0",
      "amount": "0",
      "destination": "KT1WPEis2WhAc2FciM2tZVn8qe6pCBe9HkDp",
      "parameters": {
        "prim": "Right",
        "args": [
          {
            "prim": "None"
          }
        ]
      },
      "metadata": {
        "balance_updates": [],
        "operation_result": {
          "status": "applied",
          "storage": {
            "prim": "Pair",
            "args": [
            ]
          },
          "consumed_gas": "105868",
          "storage_size": "5157"
        }
      }
    }
  ],
  "signature": "signoVkqnvViqwNSpdf8fykaguasvzCxWYQry5hPT5nciAoFYRGxsRBTLDxeeDbVDQGGtyGJGazPtWJXiXZ9pi7hjeiJMnct"
}

Answer 1

From my understanding, yes and no. There are four groups of operations:

1. Baking - endorsements
2. Voting - proposals and ballots
3. Annonymous - seed_nonce_revelation, double_bake/endorse, activate_account
4. Manager - reveal, delegation, transaction, origination

I believe you can combine different operations from the same group.