Not sure if the extra comma in your statement above is a copy and paste concern, but you have a comma between the ‘t’ and Keys. Can you check out your original statement to see if it is a comma instead of a period?
Keys.chord(Keys.ALT,Keys.SHIFT,Keys.T)
Saying that, I think you may need an object in order to “sendKeys” the combination, even if the object is to bring focus to the form. For this you may have to play with various elements. Maybe even create an object that is the top of your xpaths for those hard to reach elements, like id(“mainPage”).