old_contents: from django.db import models
  
  # Create your models here.
  
new_contents: from django.db import models
  
  
  class Bond(models.Model):
      """A Django model class for a Bond financial instrument.
  
      A bond is a financial instrument issued by the government or corporations when they need to
      borrow money from the public on a long term basis to finance certain projects. Interest payments
      called coupons are typically paid out to bond holders on a regular basis while the entire loan
      amount called the Face or Par value is repaid at the end.
  
      Attributes:
          name: The name of the bond.
          face_value: The principal of the bond to be repaid at the end of the maturity period.
          annual_coupon_rate: The stated annual interest rate for a bond.
          annual_payment_frequency: The number of coupon interest payments made annually.
          issue_date: The date the bond was issued.
          settlement_date: The date the bond is purchased.
          maturity_date: The date the bond matures.
  
      """
      name = models.CharField(max_length=128)
      face_value = models.DecimalField(max_digits=20, decimal_places=2)
      annual_coupon_rate = models.DecimalField(max_digits=5, decimal_places=4)
      annual_payment_frequency = models.IntegerField()
  
      issue_date = models.DateField()
      settlement_date = models.DateField()
      maturity_date = models.DateField()
subject: Add Bond model.