sample_position error

[QilongPan]

Thanks for sharing this code.I found an error on line 552.it lose len function.

def sample_position(self, game) -> int:
# Sample position from game either uniformly or according to some priority.
return numpy.random.choice(game.history)
I think it should be
def sample_position(self, game) -> int:
# Sample position from game either uniformly or according to some priority.
return numpy.random.choice(len(game.history))

[Zeta36]

Please, create a pull request with this fix.