code: def lock_parameter(self, name, par, lock=True):
          
          name = self.roi.get_source_by_name(name).name
          lck_params = self._lck_params.setdefault(name, [])
  
          if lock:
              self.free_parameter(name, par, False)
              if not par in lck_params:
                  lck_params += [par]
          else:
              if par in lck_params:
                  lck_params.remove(par)
docs: Set parameter to locked/unlocked state.  A locked parameter
          will be ignored when running methods that free/fix sources or
          parameters.
  
          Parameters
          ----------
          name : str
              Source name.
  
          par : str
              Parameter name.
  
          lock : bool       
              Set parameter to locked (True) or unlocked (False) state.