Fix precedence issue

trans/transpiler/__init__.py

@@ -137,7 +137,7 @@ class NodeVisitor:
 
 
 class ExpressionVisitor(NodeVisitor):
-    def __init__(self, precedence: int = 0):
+    def __init__(self, precedence: Optional[int] = None):
         self._precedence = precedence
 
     def visit_Tuple(self, node: ast.Tuple) -> Iterable[str]:
@@ -199,7 +199,7 @@ class ExpressionVisitor(NodeVisitor):
         # TODO: precedence
         op = SYMBOLS[type(op)]
         inner = ExpressionVisitor(PRECEDENCE_LEVELS[op])
-        prio = inner._precedence > self._precedence != 0
+        prio = self._precedence is not None and inner._precedence > self._precedence
         if prio:
             yield "("
         yield from inner.visit(left)