code: def relation_get(attribute=None, unit=None, rid=None):
      
      _args = ['relation-get', '--format=json']
      if rid:
          _args.append('-r')
          _args.append(rid)
      _args.append(attribute or '-')
      if unit:
          _args.append(unit)
      try:
          return json.loads(subprocess.check_output(_args).decode('UTF-8'))
      except ValueError:
          return None
      except CalledProcessError as e:
          if e.returncode == 2:
              return None
          raise
docs: Get relation information