code: def versions_from_parentdir(parentdir_prefix, root, verbose):
      
      dirname = os.path.basename(root)
      if not dirname.startswith(parentdir_prefix):
          if verbose:
              print("guessing rootdir is '%s', but '%s' doesn't start with "
                    "prefix '%s'" % (root, dirname, parentdir_prefix))
          raise NotThisMethod("rootdir doesn't start with parentdir_prefix")
      return {"version": dirname[len(parentdir_prefix):],
              "full-revisionid": None,
              "dirty": False, "error": None}
docs: Try to determine the version from the parent directory name.
  
      Source tarballs conventionally unpack into a directory that includes
      both the project name and a version string.