code: def _get_dcd(self, alias):
          
          # https://docs.docker.com/registry/spec/api/#deleting-an-image
          # Note When deleting a manifest from a registry version 2.3 or later,
          # the following header must be used when HEAD or GET-ing the manifest
          # to obtain the correct digest to delete:
          # Accept: application/vnd.docker.distribution.manifest.v2+json
          return self._request(
              'head',
              'manifests/{}'.format(alias),
              headers={'Accept': _schema2_mimetype},
          ).headers.get('Docker-Content-Digest')
docs: Get the Docker-Content-Digest header for an alias.
  
          :param alias: Alias name.
          :type alias: str
  
          :rtype: str
          :returns: DCD header for the alias.