new_contents: import matplotlib.pyplot as plt
  import numpy as np
  
  from scipy import signal
  
  f, (ax1, ax2) = plt.subplots(2, sharex=True)
  
  for i in np.linspace(0.0, 1.0, 11):
      # A linear interpolation filter with a factor of `i`.
      w, h = signal.freqz([(1.0 - i), i])
  
      # Scale x-axis to Hz.
      x = w * 44100 / (2 * np.pi)
  
      # Plot amplitude response on the dB scale.
      ax1.plot(x,  20 * np.log10(abs(h)), color='c', alpha=1.0 - i)
  
      # Plot phase response in radians.
      ax2.plot(x, np.unwrap(np.angle(h)), color='c', alpha=1.0 - i)
  
  ax1.set_title('Amplitude Response (dB)')
  ax2.set_title('Phase Response (radians)')
  
  ax2.set_yticks(np.linspace(-1.0, 0.0, 5) * np.pi)
  ax2.set_yticklabels([r'$-\pi$', r'$-\frac{3\pi}{4}$', r'$-\frac{\pi}{2}$',
      r'$-\frac{\pi}{4}$', r'$0$'])
  
  ax1.axis('tight')
  ax2.axis('tight')
  
  ax1.grid()
  ax2.grid()
  
  plt.show()
  
subject: Add exploration of linear interp filter freq response