How to do populating array of Object IDs in LB4

[noufalnoufu]

Maintainers' Note: This question has been posted elsewhere:
https://stackoverflow.com/q/66621721/5019371

How to do array populate in lb4, I found the solution in lb3 in stackoverflow,
https://stackoverflow.com/questions/51887050/loopback-relations-not-populating-array-of-object-ids

Can anybody help me on this ?
Model A :
{
id: 100,
bIdList: [200, 201]
}
Model B :
{
id: 200,
active: true
},
{
id: 201,
active: false
}
Result should be like this
{
id: 100,
bIdList: [200, 201]
bRelation: [
{
id: 200,
active: true
},
{
id: 201,
active: false }
]
}