docs: def build(self, root="runs"):
          """
          Build a nested directory structure, starting in ``root``
  
          :param root: Root directory for structure
          """
  
          for d, control in self.iter(root):
              _mkdirs(d)
              with open(os.path.join(d, self.control_name), 'w') as fp:
                  json.dump(control, fp, indent=self.indent)
                  # RJSON and some other tools like a trailing newline
                  fp.write('\n')