From 8e8263ab6c1179d46ae2ae666ef7cb08623112fc Mon Sep 17 00:00:00 2001
From: chaton <thomas@grid.ai>
Date: Thu, 19 Nov 2020 16:53:10 +0000
Subject: [PATCH] update docs (#4739)

---
 docs/source/trainer.rst | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/docs/source/trainer.rst b/docs/source/trainer.rst
index 0f9fc1fd42..a11eaceee1 100644
--- a/docs/source/trainer.rst
+++ b/docs/source/trainer.rst
@@ -1475,6 +1475,11 @@ with the hidden
             # hiddens are the hiddens from the previous truncated backprop step
             out, hiddens = self.lstm(data, hiddens)
 
+            # remember to detach() hiddens.
+            # If you don't, you will get a RuntimeError: Trying to backward through
+            # the graph a second time...
+            # Using hiddens.detach() allows each split to be disconnected.
+
             return {
                 "loss": ...,
                 "hiddens": hiddens  # remember to detach() this
@@ -1702,4 +1707,3 @@ The metrics sent to the progress bar.
 
     progress_bar_metrics = trainer.progress_bar_metrics
     assert progress_bar_metrics['a_val'] == 2
-