code: def genl_ctrl_grp_by_name(family, grp_name):
      
      for grp in nl_list_for_each_entry(genl_family_grp(), family.gf_mc_grps, 'list_'):
          if grp.name == grp_name:
              return grp.id_
      return -NLE_OBJ_NOTFOUND
docs: https://github.com/thom311/libnl/blob/libnl3_2_25/lib/genl/ctrl.c#L446.
  
      Positional arguments:
      family -- genl_family class instance.
      grp_name -- bytes.
  
      Returns:
      group ID or negative error code.