MAINT: Fix flake8 errors

Author: ghisvail

pydra/utils/hash.py

@@ -99,7 +99,8 @@ def hash_single(obj: object, cache: Cache) -> Hash:
 
 @runtime_checkable
 class HasBytesRepr(Protocol):
-    def __bytes_repr__(self, cache: Cache) -> Iterator[bytes]: ...  # pragma: no cover
+    def __bytes_repr__(self, cache: Cache) -> Iterator[bytes]:
+        pass  # pragma: no cover
 
 
 @singledispatch