def convertActionToVelocity(action):
        """ Converts the action (an integer from 0 to 8)
            to the changes in velocity in x and y
            according to the following table

                          dV_x
                    | -1    0    1
                  ----------------
                 -1 |  0    1    2
                    |
              dVy 0 |  3    4    5
                    |  
                  1 |  6    7    8

            @type action: int
                A number between 0 and 8.
            @type: tuple[int]
                The changes in x velocity and y velocity
                represented as (dV_x, dV_y)
            
        """
        if not 0 <= action <= 8:
            raise ValueError("That's not a valid action!")
        
        dV_x = action % 3 - 1
        dV_y = action // 3 - 1
        
        return dV_x, dV_y