docs: def var_cmd():
      """Print a list of available variables.
  
      See :mod:`stagpy.phyvars` where the lists of variables organized by command
      are defined.
      """
      print_all = not any(val for _, val in conf.var.opt_vals_())
      if print_all or conf.var.field:
          print('field:')
          _layout(phyvars.FIELD, phyvars.FIELD_EXTRA)
          print()
      if print_all or conf.var.sfield:
          print('surface field:')
          _layout(phyvars.SFIELD, {})
          print()
      if print_all or conf.var.rprof:
          print('rprof:')
          _layout(phyvars.RPROF, phyvars.RPROF_EXTRA)
          print()
      if print_all or conf.var.time:
          print('time:')
          _layout(phyvars.TIME, phyvars.TIME_EXTRA)
          print()
      if print_all or conf.var.plates:
          print('plates:')
          _layout(phyvars.PLATES, {})