@classmethod
def Instance(cls, xx, yy):
    if (cls.pool is None):
        cls.pool = []
        cls.pool_max_size = 10
    if (len(cls.pool) == 0):
        return PVector(xx, yy)
    else:
        v = cls.pool.pop()
        v.x = xx
        v.y = yy
        return v
@classmethod
def Instance(cls, xx, yy):
    if (cls.pool is None):
        cls.pool = []
        cls.pool_max_size = 10
    if (len(cls.pool) == 0):
        return PVector(xx, yy)
    else:
        v = cls.pool.pop()
        v.x = xx
        v.y = yy
        return v