Fix typo in documentation for collections.ChainMap, thanks to Olivier Bernard from docs@
diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index dc76ea5..7979f07 100644
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -159,7 +159,7 @@
d['x'] # Get first key in the chain of contexts
d['x'] = 1 # Set value in current context
- del['x'] # Delete from current context
+ del d['x'] # Delete from current context
list(d) # All nested values
k in d # Check all nested values
len(d) # Number of nested values