grass.script: Explain setting of debug level (#2313)

* libpython core docs: explain setting of debug level

python/grass/script/core.py

@@ -8,7 +8,7 @@
     from grass.script import core as grass
     grass.parser()
 
-(C) 2008-2021 by the GRASS Development Team
+(C) 2008-2022 by the GRASS Development Team
 This program is free software under the GNU General Public
 License (>=v2). Read the file COPYING that comes with GRASS
 for details.
@@ -737,10 +737,17 @@ def message(msg, flag=None):
 
 
 def debug(msg, debug=1):
-    """Display a debugging message using `g.message -d`
+    """Display a debugging message using `g.message -d`.
+
+    The visibility of a debug message at runtime is controlled by
+    setting the corresponding DEBUG level with `g.gisenv set="DEBUG=X"`
+    (with `X` set to the debug level specified in the function call).
 
     :param str msg: debugging message to be displayed
-    :param str debug: debug level (0-5)
+    :param str debug: debug level (0-5) with the following recommended levels:
+        Use 1 for messages generated once of few times,
+        3 for messages generated for each raster row or vector line,
+        5 for messages generated for each raster cell or vector point.
     """
     if debug_level() >= debug:
         # TODO: quite a random hack here, do we need it somewhere else too?

python/grass/temporal/temporal_topology_dataset_connector.py

@@ -3,7 +3,7 @@
 
 Usage:
 
-.. code-block:: python:
+.. code-block:: python
 
     >>> import grass.temporal as tgis
     >>> tmr = tgis.TemporalTopologyDatasetConnector()
@@ -43,7 +43,7 @@ class TemporalTopologyDatasetConnector(object):
     - finishes
     - finished
 
-    .. code-block:: python:
+    .. code-block:: python
 
         # We have build the temporal topology and we know the first map
         start = first