fix: expression hashing and repr

[tlambert03]

No description provided.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (main@b5dea46). Click here to learn what that means.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #39   +/-   ##
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  Coverage        ?   97.53%           
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  Files           ?       31           
  Lines           ?     1621           
  Branches        ?        0           
=======================================
  Hits            ?     1581           
  Misses          ?       40           
  Partials        ?        0           

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