diff --git a/src/find_pll_trng_configs.py b/src/find_pll_trng_configs.py
index 00d3d32..7e11410 100644
--- a/src/find_pll_trng_configs.py
+++ b/src/find_pll_trng_configs.py
@@ -13,6 +13,9 @@
 #   a tool to help you find configurations
 #   according to defined constraints.
 
+# update Python lib when necessary
+# pip install python-contraint
+
 from functools import lru_cache
 from math import sqrt, floor, ceil, gcd
 from time import process_time