Updates by comments

Author: AArdeev

doc/reference/reference_lua/box_index/parts.rst

@@ -13,8 +13,27 @@ index_object:parts
     :ref:`extract_key() <key_def-extract_key>`,
     :ref:`compare() <key_def-compare>`,
     :ref:`compare_with_key() <key_def-compare_with_key>`,
-    :ref:`merge() <key_def-merge>`,
-    :ref:`totable() <key_def-totable>`.
+    :ref:`merge() <key_def-merge>`.
+
+    **``index_object:parts`` example**
+
+    ..  code-block:: lua
+          
+            box.schema.space.create('T')
+            i = box.space.T:create_index('I', {parts={3, 'string', 1, 'unsigned'}})
+            box.space.T:insert{1, 99.5, 'X', nil, 99.5}
+            i.parts:extract_key(box.space.T:get({'X', 1}))
+
+    **``key_def`` equivalent**
+
+        ..  code-block:: lua
+          
+            key_def = require('key_def')
+            box.schema.space.create('T')
+            i = box.space.T:create_index('I', {parts={3, 'string', 1, 'unsigned'}})
+            box.space.T:insert{1, 99.5, 'X', nil, 99.5}
+            k = key_def.new(i.parts)
+            k:extract_key(box.space.T:get({'X', 1}))
 
     The outcome of the methods calling is described in :ref:`key_def_object <key_def_object>`.