From 0b8b3e679a1381d56924b05855e0bcb3512a5dd4 Mon Sep 17 00:00:00 2001
From: Glandos <bugs-github@antipoul.fr>
Date: Sat, 22 Dec 2018 15:29:31 +0100
Subject: [PATCH] Add code comment

---
 src/PIL/TiffTags.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/PIL/TiffTags.py b/src/PIL/TiffTags.py
index c47a88fe7..0264a6066 100644
--- a/src/PIL/TiffTags.py
+++ b/src/PIL/TiffTags.py
@@ -29,6 +29,9 @@ class TagInfo(namedtuple("_TagInfo", "value name type length enum")):
             cls, value, name, type, length, enum or {})
 
     def cvt_enum(self, value):
+        # Using get will call hash(value), which can be expensive
+        # for some types (e.g. Fraction). Since self.enum is rarely
+        # used, it's usually better to test it first.
         return self.enum.get(value, value) if self.enum else value