code: def __add_images_to_manifest(self):
          
  
          xpath_expr = "//manifest:manifest[1]"
  
          for content_tree in self.content_trees:
  
              # Find manifest:manifest tags.
              manifest_e = content_tree.xpath(
                  xpath_expr,
                  namespaces=self.namespaces
              )
              if not manifest_e:
                  continue
  
              for identifier in self.images.keys():
                  # Add a manifest:file-entry tag.
                  lxml.etree.SubElement(
                      manifest_e[0],
                      '{%s}file-entry' % self.namespaces['manifest'],
                      attrib={
                          '{%s}full-path' % self.namespaces['manifest']: (
                              PY3O_IMAGE_PREFIX + identifier
                          ),
                          '{%s}media-type' % self.namespaces['manifest']: '',
                      }
                  )
docs: Add entries for py3o images into the manifest file.