def __init__(self, start_pos, dt):
        """
        Initialize the tennis ball position and set the movement rate
        """
        self.x, self.y = start_pos
        self.dx = self.dy = dt
def __init__ ( self , start_pos , dt ) : self . x , self . y = start_pos self . dx = self . dy = dt
Initialize the tennis ball position and set the movement rate