code: def deregister_image(self, image_id, delete_snapshot=False):
          
          snapshot_id = None
          if delete_snapshot:
              image = self.get_image(image_id)
              for key in image.block_device_mapping:
                  if key == "/dev/sda1":
                      snapshot_id = image.block_device_mapping[key].snapshot_id
                      break
  
          result = self.get_status('DeregisterImage',
                                   {'ImageId':image_id}, verb='POST')
          if result and snapshot_id:
              return result and self.delete_snapshot(snapshot_id)
          return result
docs: Unregister an AMI.
  
          :type image_id: string
          :param image_id: the ID of the Image to unregister
  
          :type delete_snapshot: bool
          :param delete_snapshot: Set to True if we should delete the
                                  snapshot associated with an EBS volume
                                  mounted at /dev/sda1
  
          :rtype: bool
          :return: True if successful