Report the closest (via fuzzy match) pairs on unmatched input

piker/brokers/deribit/api.py

@@ -28,8 +28,9 @@ from decimal import (
     Decimal,
 )
 from functools import partial
-import time
 from pathlib import Path
+from pprint import pformat
+import time
 from typing import (
     Any,
     Optional,
@@ -369,6 +370,19 @@ class Client:
             return cached_pair
 
         if sym:
+            opt: OptionPair|None = pair_table.get(sym)
+            if not opt:
+                closest_matches: dict[str, Pair] = match_from_pairs(
+                    pairs=pair_table,
+                    query=sym,
+                    score_cutoff=40,
+                )
+                closest_syms: list[str] = list(closest_matches.keys())
+                raise ValueError(
+                    f'No contract found for {sym!r}\n\n'
+                    f'Closest {len(closest_syms)} available contracts:\n\n'
+                    f'{pformat(closest_syms)}\n'
+                )
             return pair_table[sym]
         else:
             return self._pairs