139 def groupbyfoldid(predsets):

   140     """ Group nodes and related obsmarkers by fold-id metadata.

   141     """

   142     groups = {}

   143     for (nodes, markers) in predsets:

   144         grouped = False

   145         for marker in markers:

   146             metadata = dict(marker[3])

   147             foldid = metadata.get(b'fold-id')

   148             if foldid is not None:

   149                 groups.setdefault(foldid, []).append((nodes, markers))

   150                 grouped = True

   151 

   152         if not grouped:

   153             yield (nodes, markers)

   154 

   155     for foldid in sorted(groups):

   156         groupnodes = set()

   157         groupmarkers = set()

   158         for (nodes, markers) in groups[foldid]:

   159             groupnodes.update(nodes)

   160             groupmarkers.update(markers)

   161         yield (tuple(sorted(groupnodes)), tuple(sorted(groupmarkers)))

   162