Slider ticks in pavlovia online experiment

I want the ticks on the slider to not show up expect for in the ends. I found the code in the discourse and modified it :
for i in range (1,99):
slider_2.tickLines.sizes[i][1] = 0
slider_2.tickLines._needVertexUpdate = True

However, this code does not work whenever I run the experiment online, The error is: TypeError: Cannot read properties of undefined (reading ‘sizes’). I also cannot find a substitute for the _needVertexUpdate = true part.