walk() docs: Emphasize that the recursive-delete example is dangerous.
diff --git a/Doc/lib/libos.tex b/Doc/lib/libos.tex
index 6a1223f..c9cf137 100644
--- a/Doc/lib/libos.tex
+++ b/Doc/lib/libos.tex
@@ -1126,6 +1126,8 @@
import os
from os.path import join
# Delete everything reachable from the directory named in 'top'.
+# CAUTION: This is dangerous! For example, if top == '/', it
+# could delete all your disk files.
for root, dirs, files in os.walk(top, topdown=False):
for name in files:
os.remove(join(root, name))