"bash: [: =: unary operator expected" on Linux for Robotics course

Course Support Linux Basics For Robotics
7

Hi
i am having the same problem using the copy paste of the code from the course:
#!/bin/bash

ARG1=$1

if [ $ARG1 == 'forward' ]; then
    rostopic pub /cmd_vel geometry_msgs/Twist "linear:
  x: -0.1
  y: 0.0
  z: 0.0
angular:
  x: 0.0
  y: 0.0
  z: 0.0"

elif [ $ARG1 == 'rotate' ]; then
    rostopic pub /cmd_vel geometry_msgs/Twist "linear:
  x: 0.0
  y: 0.0
  z: 0.0
angular:
  x: 0.0
  y: 0.0
  z: 0.2"

elif [ $ARG1 == 'stop' ]; then
    rostopic pub /cmd_vel geometry_msgs/Twist "linear:
  x: 0.0
  y: 0.0
  z: 0.0
angular:
  x: 0.0
  y: 0.0
  z: 0.0"
fi

i get the folowing:
./demo.sh: line 5: [: ==: unary operator expected
./demo.sh: line 15: [: ==: unary operator expected
./demo.sh: line 25: [: ==: unary operator expected

i was having the same isue in the exam took me a while to trial and error what was wrong i think it has something to do with spaces? but since it is in a course a copy paste should work?