#可视化sigmoid函数代码import numpy as np import matplotlib.pyplot as plt   def sigmoid(x):     return 1. / (1. + np.exp(-x))   def plot_sigmoid():     x = np.arange(-10, 10, 0.1)     y = sigmoid(x)     plt.plot(x, y, label="sigmoid")     plt.legend()     plt.title("nowcoder: offer+1")     plt.show()   def main():     plot_sigmoid()  if __name__ == '__main__':     main()