text: import numpy as np
  import matplotlib.pyplot as plt
  
  x = np.linspace(-3, 3, 100)
  
  tanh = np.tanh(x)
  def sigmoid(_x):
      return 1 / (1+np.exp(-_x))
  sig = sigmoid(x)
  relu = np.clip(x, 0, None)
  
  plt.plot(x, tanh, label='tanh', lw=4)
  plt.plot(x, sig, label='sigmoid', lw=4)
  plt.plot(x, relu, label='ReLU', lw=4)
  plt.axhline(-1, ls='--', c='black')
  plt.axhline(0, ls='--', c='black')
  plt.axhline(1, ls='--', c='black')
  plt.axvline(0, ls='--', c='black')
  plt.ylim([-1, 1])
  plt.xticks(list(range(-3, 4)))
  plt.yticks([-1, -.5, 0, .5, 1])
  plt.legend()
  plt.show()
  