I have a list of dictionaries that look like this:

```
[
  {
    'accountId': 952940,
    'objectType': 'Creative',
    'objectId': 1361295595
  },
  {
    'accountId': 7037,
    'objectType': 'Placement',
    'objectId': 2713583698
  },
  {
    'accountId': 7037,
    'objectType': 'Placement',
    'objectId': 271354409
  },
  {
    'accountId': 7037,
    'objectType': 'Ad',
    'objectId': 1234565698
  }
]

```

I want to group them by accountId and objectType, so the final output looks like this:

```
[
  {
    'accountId': 959740,
    'objectType': 'Creative',
    'objectId': 136139595
  },
  {
    'accountId': 7037,
    'objectType': 'Placement',
    'objectId': [275765698,279984409]
  },
  {
    'accountId': 7037,
    'objectType': 'Ad',
    'objectId': 1234565698
  }
]

```

Any help would be appreciated.