def __init__(self, num_kp=21):
    self.data = list()
    self.num_kp = num_kp
    for _ in range(num_kp):
        self.data.append(list())
def __init__(self, num_kp=21):
    self.data = list()
    self.num_kp = num_kp
    for _ in range(num_kp):
        self.data.append(list())