code: def join(cls, diffs: Iterable['DBDiff']) -> 'DBDiff':
          
          tracker = DBDiffTracker()
          for diff in diffs:
              diff.apply_to(tracker)
          return tracker.diff()
docs: Join several DBDiff objects into a single DBDiff object.
  
          In case of a conflict, changes in diffs that come later
          in ``diffs`` will overwrite changes from earlier changes.