Unity doesn't see UnityEngine.XR.MagicLeap Contents?

I'm trying to implement the script for ML1 to recognize gestures and I followed the examples provided in the SDK documentation. When I try to run the project, Unity says that 'The type or namespace name 'InputSubsystem' could not be found (are you missing a using directive or an assembly reference?)'. If I understand correctly, the InputSubsystem should be available when you have the following using statement:

using UnityEngine.XR.MagicLeap;

I also have following using statements that I took from documentation:

using InputDevice = UnityEngine.XR.InputDevice;
using HandGestures = InputSubsystem.Extensions.DeviceFeatureUsages.HandGesture;
using GestureClassification = InputSubsystem.Extensions.MLGestureClassification;

I don't understand why it doesn't work. Am I missing something?

Environment: Lumin SDK - 0.26.0
Magic Leap 1 - 0.98.30 OS
Unity - 2020.3
API Level - 10
Windows 10

Hi @ashepelev It looks like you are using Magic Leap 2 documentation when Developing on Magic Leap 1. Please see the Developer Portal | Magic Leap for Magic Leap 1 documentation and submit Magic Leap 1 related questions here : https://forum.magicleap.com/hc/en-us/community/topics