after.json

{
  "type": "multiple_choice_field",
  "key": "multiple_choice_field-result_list-0",
  "index": "0",
  "value": "Default Choice",
  "sub_index": null
},
{
  "type": "multiple_choice_field",
  "key": "multiple_choice_field-result_list-0",
  "index": "0",
  "value": "Second Choice",
  "sub_index": null
}

before.json

{
  "type": "multiple_choice_field",
  "key": "multiple_choice_field-result_list-0",
  "index": "0",
  "value": "['Default Choice', 'Second Choice']",
  "sub_index": null
}