code: def _get_shells():
      '''
      Return the valid shells on this system
      '''
      start = time.time()
      if 'sh.last_shells' in __context__:
          if start - __context__['sh.last_shells'] > 5:
              __context__['sh.last_shells'] = start
          else:
              __context__['sh.shells'] = __salt__['cmd.shells']()
      else:
          __context__['sh.last_shells'] = start
          __context__['sh.shells'] = __salt__['cmd.shells']()
      return __context__['sh.shells'f _get_shells():
      '''
      Return the valid shells on this system
      '''
      start = time.time()
      if 'sh.last_shells' in __context__:
          if start - __context__['sh.last_shells'] > 5:
              __context__['sh.last_shells'] = start
          else:
              __context__['sh.shells'] = __salt__['cmd.shells']()
      else:
          __context__['sh.last_shells'] = start
          __context__['sh.shells'] = __salt__['cmd.shells']()
      return __context__['sh.shells']
docs: Return the valid shells on this system