Add "sum" to DUPLICATE_POLICY documentation of TS.CREATE, TS.ADD and TS.ALTER

CHANGES

@@ -55,6 +55,7 @@
     * Fix for Unhandled exception related to self.host with unix socket (#2496)
     * Improve error output for master discovery 
     * Make `ClusterCommandsProtocol` an actual Protocol
+    * Add `sum` to DUPLICATE_POLICY documentation of `TS.CREATE`, `TS.ADD` and `TS.ALTER`
 
 * 4.1.3 (Feb 8, 2022)
   * Fix flushdb and flushall (#1926)

redis/commands/timeseries/commands.py

@@ -59,6 +59,9 @@ def create(
             - 'last': override with latest value.
             - 'min': only override if the value is lower than the existing value.
             - 'max': only override if the value is higher than the existing value.
+            - 'sum': If a previous sample exists, add the new sample to it so that \
+            the updated value is equal to (previous + new). If no previous sample \
+            exists, set the updated value equal to the new value.
 
         For more information: https://redis.io/commands/ts.create/
         """  # noqa
@@ -103,6 +106,9 @@ def alter(
             - 'last': override with latest value.
             - 'min': only override if the value is lower than the existing value.
             - 'max': only override if the value is higher than the existing value.
+            - 'sum': If a previous sample exists, add the new sample to it so that \
+            the updated value is equal to (previous + new). If no previous sample \
+            exists, set the updated value equal to the new value.
 
         For more information: https://redis.io/commands/ts.alter/
         """  # noqa
@@ -154,6 +160,9 @@ def add(
             - 'last': override with latest value.
             - 'min': only override if the value is lower than the existing value.
             - 'max': only override if the value is higher than the existing value.
+            - 'sum': If a previous sample exists, add the new sample to it so that \
+            the updated value is equal to (previous + new). If no previous sample \
+            exists, set the updated value equal to the new value.
 
         For more information: https://redis.io/commands/ts.add/
         """  # noqa