我是编程新手，正在完成一门关于自动驾驶汽车的课程。这是我的作业代码（纵向车辆模型）。我已经在注释（#）中尝试解释了代码。我遇到了以下错误：

类Bicycle未定义。

代码如下：

from notebook_grader import BicycleSolution, grade_bicycleimport numpy as npimport matplotlib.pyplot as pltimport matplotlib.image as mpimgclass Bicycle():    def __init__(self):    self.xc = 0    self.yc = 0    self.theta = 0    self.delta = 0    self.beta = 0    self.L = 2    self.lr = 1.2    self.w_max = 1.22    self.sample_time = 0.01def reset(self):    self.xc = 0    self.yc = 0    self.theta = 0    self.delta = 0    self.beta = 0class Bicycle(Bicycle):    def step(self, v, w):    # ==================================    #  Implement kinematic model here    # ==================================    #so that max rate is not exceeded    if w > 0:        w = min(w, self.w_max)    else:        w = max(w, -self.w_max)    #sampling time    t_sample = 10e-3    #implementing the differential equations    xc_dot = v * np.cos(self.theta + self.beta)    yc_dot = v * np.sin(self.theta + self.beta)    theta_dot = (v / self.L) * (np.cos(self.beta) * np.tan(self.delta))    delta_dot = w    self.beta = np.arctan(self.lr * np.tan(self.delta) / self.L)    #update equations using the sampling time    self.xc += xc_dot * t_sample    self.yc += yc_dot * t_sample    self.theta += theta_dot * t_sample     self.delta += delta_dot * t_sample

回答：

您定义了两个冲突的类：父类和子类都是”Bicycle”。请尝试重命名它们。