Limit rotation on the Y axis Godot

Player scene structure

+ Player
  - Body
    - MeshInstance
  - Head
    - Camera

Player.gd

extends KinematicBody

export var speed = 10
export var acceleration = 5
export var gravity = 0.98
export var jump_power = 30
export var mouse_sensitivity = 0.3

onready var head = $Head
onready var camera = $Head/Camera
onready var body = $Body;

var velocity = Vector3()

func _ready():
	Input.set_mouse_mode(Input.MOUSE_MODE_CAPTURED)

func _input(event):
	if(paused):
		return;

	if event is InputEventMouseMotion:
		# Rotate the whole player instead of just the head.
		head.rotate_y(deg2rad(-event.relative.x * mouse_sensitivity));
		camera.rotate_x(deg2rad(-event.relative.y * mouse_sensitivity));

		# We can make use of the rotation_degrees property and the method clamp 
		var cam_rotation = camera.rotation_degrees;
		cam_rotation.x = clamp(cam_rotation.x, -90, 90);
		camera.rotation_degrees = cam_rotation;
    
    #  Limit looking far right/left too
		var head_rotation = head.rotation_degrees;
		head_rotation.y = clamp(head_rotation.y, -90, 90);
		head.rotation_degrees = head_rotation;

func _process(delta):
  if Input.is_action_just_pressed("ui_cancel"):
    Input.set_mouse_mode(Input.MOUSE_MODE_VISIBLE);

func _physics_process(delta):
  var head_basis = head.get_global_transform().basis;

	var direction = Vector3();
	if Input.is_action_pressed("move_forward"):
		direction -= head_basis.z;
    
    # When player moves forward. Rotate body to be in the same direction as the head/camera
		if(head.rotation.y != 0):
			var y_direction = head.global_transform.basis.get_euler().y;
      
      # Reset body and head rotation and rotate the whole Player now. 
			body.rotation.y = 0;
			head.rotation.y = 0;
			self.rotation.y = y_direction;
	elif Input.is_action_pressed("move_backward"):
		direction += head_basis.z

	if Input.is_action_pressed("move_left"):
		direction -= head_basis.x
	elif Input.is_action_pressed("move_right"):
		direction += head_basis.x

	direction = direction.normalized()

	velocity = velocity.linear_interpolate(direction * speed, acceleration * delta)
	velocity.y -= gravity
	
	if Input.is_action_just_pressed("move_jump") and is_on_floor():
		velocity.y += jump_power
	
	velocity = move_and_slide(velocity, Vector3.UP)