docs: def _expand_description(desc):
      """Expand the description given the group names/patterns
      e.g:
      {src: grp[1-3], dst: grp[4-6] ...} will generate 9 descriptions
      """
      srcs = expand_groups(desc['src'])
      dsts = expand_groups(desc['dst'])
      descs = []
      for src in srcs:
          for dst in dsts:
              local_desc = desc.copy()
              local_desc['src'] = src
              local_desc['dst'] = dst
              descs.append(local_desc)
  
      return descs