code: def delete_before(self, segment_info):
          
  
          # This will delete all base backup data before segment_info.
          self._delete_base_backups_before(segment_info)
  
          # This will delete all WAL segments before segment_info.
          self._delete_wals_before(segment_info)
  
          if self.deleter:
              self.deleter.close()
docs: Delete all base backups and WAL before a given segment
  
          This is the most commonly-used deletion operator; to delete
          old backups and WAL.