Not clear why JSON response receives an auto-generated key

**Describe the bug**
When calling the method `result = sg.query_json()`, the returned object looks roughly like this:

```
$result
[{'xcfb7c9c5f581c978': [{"title":"title1", "id":1}, {"title":"title2",id":2}
```

It's not clear to me (also could not find anything in the docs) why the results are indexed by this (apparently random) key. Isn't it easier to just return all flattened items?
I apologize if this behaviour is documented somewhere.

**To Reproduce**
- Query this subgraph https://api.thegraph.com/subgraphs/name/protofire/omen-xdai/graphql?query=query+%7B%0A++fixedProductMarketMakers%28first%3A2%2C%0A++++where%3A+%7B%0A++++++outcomes%3A+%5B%22Yes%22%2C%22No%22%5D%0A++++%7D%0A++%29+%7B%0A++++id%0A++++outcomes%0A++%7D%0A%7D (fetching `fixedProductMarketMakers`)

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Desktop (please complete the following information):**
- OS: [e.g. iOS]
- Browser [e.g. chrome, safari]
- Version [e.g. 22]

**Python version (please complete the following information):**
- 3.10.13

Look at the sg.query_json() method in the subgrounds library to understand how GraphQL responses are processed. The issue mentions a random key in the JSON output; examine the response transformation logic. Check if there are existing tests for query_json to see the expected structure. Determine if the key is necessary for nested data or if results can be flattened as suggested.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.