Added expiry property for OptionPair

piker/brokers/deribit/venues.py

@@ -116,6 +116,12 @@ class OptionPair(Pair, frozen=True, kw_only=True):
     # NOTE: see `.data._symcache.SymbologyCache.load()` for why
     ns_path: str = 'piker.brokers.deribit:OptionPair'
 
+    @property
+    def expiry(self) -> str:
+        symbol: str = self.instrument_name.lower()
+        pair, expiry, strike_price, otype = symbol.split('-')
+        return f'{expiry}'
+
     @property
     def venue(self) -> str:
         return 'OPTION'