code: def _merge_pool_kwargs(self, override):
          
          base_pool_kwargs = self.connection_pool_kw.copy()
          if override:
              for key, value in override.items():
                  if value is None:
                      try:
                          del base_pool_kwargs[key]
                      except KeyError:
                          pass
                  else:
                      base_pool_kwargs[key] = value
          return base_pool_kwargs
docs: Merge a dictionary of override values for self.connection_pool_kw.
  
          This does not modify self.connection_pool_kw and returns a new dict.
          Any keys in the override dictionary with a value of ``None`` are
          removed from the merged dictionary.