Update devito/ir/iet/nodes.py

Co-authored-by: Ed Caunt <ed@devitocodes.com>

Author: JDBetteridge

devito/ir/iet/nodes.py

@@ -1590,7 +1590,7 @@ def __init__(self, body, halo_scheme):
         self._halo_scheme = halo_scheme
 
     def __repr__(self):
-        functions = "({})".format(",".join(i.name for i in self.functions))
+        functions = f"({','.join(i.name for i in self.functions)})"
         return f"<{self.__class__.__name__}{functions}>"
 
     @property