diff --git a/examples/how_to_write_docstring.py b/examples/how_to_write_docstring.py
index 3228de5ceb5c484bf1378b425ae22d0e7092ea13..be57e9b44147fa1e9ce3e0b5b30fff92314f1b5d 100644
--- a/examples/how_to_write_docstring.py
+++ b/examples/how_to_write_docstring.py
@@ -30,5 +30,9 @@ def cos(x: float = 0.):
     --------
     >>> import numpy as np
     >>> cos(np.pi)
+
+    Notes
+    -----
+    this function is a warpper of `numpy.cos()`
     """
     return np.cos(x)