Fix the Introduction Example

[yayami3]

Fixed small typo in Introduction Example raising error.

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[codecov]

Codecov Report

Merging #477 (3989c66) into main (017f441) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #477   +/-   ##
=======================================
  Coverage   99.16%   99.16%           
=======================================
  Files          48       48           
  Lines        1914     1914           
=======================================
  Hits         1898     1898           
  Misses         16       16           

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[rlouf]

Thank you!