Adjust topic hz and bw command description. (#987)

* Adjust topic hz and bw command description.

Signed-off-by: Tomoya Fujita <[email protected]>

* note description fix.

Signed-off-by: Tomoya Fujita <[email protected]>

* address flake8 warnings.

Signed-off-by: Tomoya Fujita <[email protected]>

---------

Signed-off-by: Tomoya Fujita <[email protected]>

Author: fujitatomoya

ros2topic/ros2topic/verb/bw.py

@@ -62,6 +62,13 @@ class BwVerb(VerbExtension):
     """Display bandwidth used by topic."""
 
     def add_arguments(self, parser, cli_name):
+        parser.description = (
+            'Display bandwidth used by topic.\n\n'
+            'note:\n'
+            '  This bandwidth reflects the receiving rate on subscription, '
+            'which might be affected by platform resources and QoS configuration, '
+            "and may not exactly match the publisher's bandwidth."
+        )
         arg = parser.add_argument(
             'topic_name',
             help='Topic name to monitor for bandwidth utilization')

ros2topic/ros2topic/verb/hz.py

@@ -54,9 +54,16 @@
 
 
 class HzVerb(VerbExtension):
-    """Print the average publishing rate to screen."""
+    """Print the average receiving rate to screen."""
 
     def add_arguments(self, parser, cli_name):
+        parser.description = (
+            'Print the average receiving rate to screen.\n\n'
+            'note:\n'
+            '  This rate reflects the receiving rate on subscription, '
+            'which might be affected by platform resources and QoS configuration, '
+            "and may not exactly match the publisher's rate."
+        )
         arg = parser.add_argument(
             'topic_name',
             nargs='+',