If you try to execute "_composer dump-autoload --optimize_", you will get the following warn

Generating optimized autoload files
Warning: Ambiguous class resolution, "StashSessionSessionHandlerInterface" was found in both
"/var/www/sites/5.4/vendor/tedivm/stash/src/Stash/Session/SessionHandlerInterface_Legacy.php"
and "/var/www/sites/5.4/vendor/tedivm/stash/src/Stash/Session/SessionHandlerInterface_Modern.php",
the first will be used.

Please add a note in Using composer documentation page explaining:

1. If such warnings can be ignored
2. If it's advisable or not to use "_composer dump-autoload --optimize_" and why

Warning is caused by https://github.com/tedious/Stash/issues/181