input: Write a python function to plot open and close prices of a stock using matplotlib.
  assert plot_stock_prices([112.22, 113.45, 114.98, 111.76, 112.35, 108.91, 111.65], [114.72, 114.22, 115.46, 111.75, 112.31, 109.30, 111.33]) is None
  assert plot_stock_prices([120.10, 121.50, 119.70], [119.50, 120.80, 118.90]) is None
output: def plot_stock_prices(open_prices, close_prices):
      import matplotlib.pyplot as plt
      
      days = range(1, len(open_prices) + 1)
      
      plt.figure(figsize=(10, 5))
      plt.plot(days, open_prices, marker='o', linestyle='-', color='b', label='Open Prices')
      plt.plot(days, close_prices, marker='o', linestyle='-', color='r', label='Close Prices')
      
      plt.xlabel('Days')
      plt.ylabel('Prices')
      plt.title('Stock Open and Close Prices')
      plt.legend()
      plt.grid(True)
      plt.show()