Can someone please validate something for me? I am seeing this behavior in both Maya 2018 and 2019 on Windows 10 and Mac...
I am trying to build a UI that has the timeline controls from Maya. Something like this:

From the help docs it appears the solution to my issue would be the timePort and rangeControl commands. However, when I execute this simple snippet I get a blank window. Can you please try this in your Maya to see if this is a bug or if I have something wrong with the code? Is there something more to these commands in order to use them in a custom UI?
from maya import cmds
cmds.window( w=500, h=35, title="Timeline Controls UI" )
cl = cmds.columnLayout(adjustableColumn=True)
cmds.rangeControl( 'myRangeSlider', minRange=0, maxRange=60, parent=cl, backgroundColor=(1,0,0))
cmds.timePort( 'myTimePort', parent=cl, backgroundColor=(0,1,0) )
cmds.showWindow()