Apply suggestions from code review

Co-authored-by: Andrew Williamson <awilliamson@mozilla.com>

Author: eemeli

fluent.runtime/fluent/runtime/bundle.py

@@ -37,10 +37,7 @@ def __init__(self,
                  functions: Union[Dict[str, Callable[[Any], 'FluentType']], None] = None,
                  use_isolating: bool = True):
         self.locales = locales
-        _functions = BUILTINS.copy()
-        if functions:
-            _functions.update(functions)
-        self._functions = _functions
+        self._functions = {**BUILTINS, **(functions or {})}
         self.use_isolating = use_isolating
         self._messages: Dict[str, Union[FTL.Message, FTL.Term]] = {}
         self._terms: Dict[str, Union[FTL.Message, FTL.Term]] = {}

fluent.syntax/fluent/syntax/visitor.py

@@ -25,7 +25,7 @@ def visit(self, node: Any) -> None:
         visit(node)
 
     def generic_visit(self, node: BaseNode) -> None:
-        for _propname, propvalue in vars(node).items():
+        for propvalue in vars(node).values():
             self.visit(propvalue)