code: def build_bootdisk(self, image, size=10, auto_delete=True):
          
          if image is None:
              raise ComputeEngineManagerException("Image must not be None.")
          return {
              'boot': True,
              'autoDelete': auto_delete,
              'initializeParams': {
                  'sourceImage': "projects/cos-cloud/global/images/{}".format(image),
                  'diskSizeGb': size,
              }
          }
docs: Buid a disk struct.
  
          :param  image: Base image name.
          :type   image: ``str``
  
          :param  size: Persistent disk size.
          :type   size: ``int``
  
          :param  auto_delete: Wether to auto delete disk on instance termination.
          :type   auto_delete: ``bool``