fix tostring bug for sweepable pipeline

[LittleLittleCloud]

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[codecov]

Codecov Report

Merging #6610 (c9f4c88) into main (4a02a01) will decrease coverage by 0.01%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6610      +/-   ##
==========================================
- Coverage   68.44%   68.43%   -0.01%     
==========================================
  Files        1176     1176              
  Lines      248210   248210              
  Branches    25915    25915              
==========================================
- Hits       169893   169871      -22     
- Misses      71559    71585      +26     
+ Partials     6758     6754       -4     

Flag	Coverage Δ
Debug	68.43% <ø> (-0.01%)	⬇️
production	62.83% <ø> (-0.02%)	⬇️
test	88.87% <ø> (ø)

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see 3 files with indirect coverage changes