Command sample that works

robot.py

import wpilib
from wpilib.buttons import JoystickButton
from wpilib.command import Command, CommandGroup, Scheduler

class DoTheThing(Command):
    def  __init__(self, robot):
        super().__init__()
        self.robot = robot

    def execute(self):
        print("DOING IT")

    def end(self):
        print("I do get called")

    def isFinished(self):
        return False

    def interrupted(self):
        print("interrupted!")
        self.end()

    def cancel(self):
        self.end()
        super().cancel()
        

class DoAllThings(CommandGroup):
    def __init__(self, robot):
        super().__init__()
        self.robot = robot
        self.addSequential(DoTheThing(self.robot))
        

class CancelCommand(Command):
    def __init__(self, thing):
        super().__init__()
        self.thing = thing
        
    def execute(self):
        print("cancelling the task")
        self.thing.cancel()
        
    def isFinished(self):
        return True
        


class MyRobot(wpilib.IterativeRobot):

    def robotInit(self):
        
        self.group = DoAllThings(self)
        
        self.joy = wpilib.Joystick(0)
        button = JoystickButton(self.joy, 1)
        button.whenPressed(self.group)
        
        button = JoystickButton(self.joy, 2)
        button.whenPressed(CancelCommand(self.group))
        
    def teleopPeriodic(self):
        """This function is called periodically during operator control."""
        Scheduler.getInstance().run()

    def testPeriodic(self):
        """This function is called periodically during test mode."""
        wpilib.LiveWindow.run()

if __name__ == "__main__":
    wpilib.run(MyRobot)