move trades_get_pairs to parent class

freqtrade/data/history/idatahandler.py

@@ -152,13 +152,17 @@ class IDataHandler(ABC):
         """
 
     @classmethod
-    @abstractmethod
     def trades_get_pairs(cls, datadir: Path) -> List[str]:
         """
         Returns a list of all pairs for which trade data is available in this
         :param datadir: Directory to search for ohlcv files
         :return: List of Pairs
         """
+        _ext = cls._get_file_extension()
+        _tmp = [re.search(r'^(\S+)(?=\-trades.' + _ext + ')', p.name)
+                for p in datadir.glob(f"*trades.{_ext}")]
+        # Check if regex found something and only return these results to avoid exceptions.
+        return [cls.rebuild_pair_from_filename(match[0]) for match in _tmp if match]
 
     @abstractmethod
     def trades_store(self, pair: str, data: TradeList) -> None: