Use of square bracket for class instance

In kotlin i am surprised to see the sqaure bracket while creating an instance of PackagePermissionsLiveData
Can someone explain how is that possible, PackagePermissionsLiveData is a class and not an array
val pkgPermGroups: Map<String, List>? = PackagePermissionsLiveData[packageName, user]

Source code : Line 80 Blame - PermissionController/src/com/android/permissioncontroller/permission/service/AutoRevokePermissions.kt - platform/packages/modules/Permission - Git at Google

Any class can implement operator fun get(…), which in turn can be called using square brackets.

:grinning: Thanks