code: def update_params(old_params, new_params, check=False):
      
      updated_params = dict(old_params)
      if new_params:  # allow for new_params to be None
          for key, val in new_params.items():
              if key not in old_params and check:
                  raise ValueError('\'' + key
                                   + '\' is not a valid parameter key, '
                                   + 'consider one of \n'
                                   + str(list(old_params.keys())))
              if val is not None:
                  updated_params[key] = val
      return updated_params
docs: Update old_params with new_params.
  
      If check==False, this merely adds and overwrites the content of old_params.
  
      If check==True, this only allows updating of parameters that are already
      present in old_params.
  
      Parameters
      ----------
      old_params : dict
      new_params : dict
      check : bool, optional (default: False)
  
      Returns
      -------
      updated_params : dict