code: def children(self):
          
          for child in self.data.get('children', []):
              if osp.exists(osp.join(self.path, child, YAML_REPORT_FILE)):
                  yield child, self.__class__(osp.join(self.path, child))
docs: get children node referenced as `children` in the
          report.
          :rtype: dict with name (str) -> node (ReportNode)