new_contents: """Plot to test text"""
  import matplotlib.pyplot as plt
  import numpy as np
  
  def main():
      fig, ax = plt.subplots()
      ax.grid(color='lightgray')
  
      x = np.linspace(0, 4 * np.pi, 1000)
      y1 = 0.5 * np.sin(0.5 * x)
      y2 = np.sin(x)
      y3 = np.cos(x)
  
      ax.fill(x, y1, alpha=0.3, facecolor='green')
      ax.fill_between(x, y2, y3, alpha=0.3, facecolor='red')
      ax.fill_between(x, -y2, -y3, alpha=0.3, facecolor='blue')
  
      ax.set_xlim(0, 4 * np.pi)
      ax.set_ylim(-1.1, 1.1)
  
      return fig
  
  if __name__ == '__main__':
      main()
      plt.show()
  
subject: add test plot test_fill.py