How to use Float32MultiArray (Publisher)

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Hello,
I am trying to write a python code using the Float32MultiArray to run my robot's motors.

The code is below:

motor = rospy.Publisher('encoder', Float32MultiArray, queue_size = 2)

while not rospy is shutdown():

    arg = Float32MultiArray()
    arg.layout.dim[0].label ="x"
    arg.layout.dim[0].size = 1
    arg.layout.dim[0].stride = 1

    arg.layout.dim[1].label ="y"
    arg.layout.dim[1].size = 1
    arg.layout.dim[1].stride = 1

    arg.layout.data_offset = 1
    arg.data = [100, 100]

    motor.publish(arg)

However, I have the error below:

TypeError: Invalid number of arguments, arg should be ['layout','data'] args are(0.0)

Could you please help me ?

Thank you in advance,

Shanika