Additional of Stopwatch to Raspberry Pi Project (using Python & Tkinter)

The existing project is a simple step counter written in Python on the Raspberry Pi. The interface is a full screen GUI user interface using Tkinter. See Screenshot. At the minute the project works as a simple step counter. There are two sensors attached to BCM5 and BCM6 (pulled up high) which when triggered pull the pins low. A step is recorded when two steps are made - a left step followed by a right step or a right step followed by a left step depending on which foot the person started using. The code behind the two pins uses event detection. We wish to add a stopwatch to this code. See attached image. Whenever "Start Test" is clicked the Step Counter is reset to 0 and the stopwatch starts counting. The stopwatch should show minutes and seconds in the format 00:00 and should be updated so that every second is indicated. To the right of the "Start Test" button you will add an additional button "Stop Test". This will prevent the Step Counter from being incremented and will pause the time on the clock. We will provide you with the existing code as a .py file. For testing purposes simple switches are perfectly acceptable on BCM5 and BCM6...we will not be providing any hardware. You will deliver the amended code containing the additional button for "Stop Test" and the label for "Time Elapsed" with the stopwatch which will update at least every second. Your code should be fully commented and where possible functions should be used.