code: def truncate_repeated_single_step_traversals(match_query):
      
      # Such traversals frequently happen as side-effects of the lowering process
      # of Backtrack blocks, and needlessly complicate the executed queries.
      new_match_traversals = []
      visited_locations = set()
  
      for current_match_traversal in match_query.match_traversals:
          ignore_traversal = False
          if len(current_match_traversal) == 1:
              # Single-step traversal detected. If its location was visited already, ignore it.
              single_step = current_match_traversal[0]
              if single_step.as_block is None:
                  raise AssertionError(u'Unexpectedly found a single-step traversal with no as_block:'
                                       u' {} {}'.format(current_match_traversal, match_query))
  
              if single_step.as_block.location in visited_locations:
                  # This location was visited before, omit the traversal.
                  ignore_traversal = True
  
          if not ignore_traversal:
              # For each step in this traversal, mark its location as visited.
              for step in current_match_traversal:
                  if step.as_block is not None:
                      visited_locations.add(step.as_block.location)
  
              new_match_traversals.append(current_match_traversal)
  
      return match_query._replace(match_traversals=new_match_traversals)
docs: Truncate one-step traversals that overlap a previous traversal location.