black, python: improved clarity of some statements

pages/common/black.md

@@ -9,13 +9,13 @@
 
 - Format the code passed in as a string:
 
-`black -c {{path/to/file_or_directory}}`
+`black -c "{{code}}"`
 
-- Output a diff for each file on stdout:
+- Output the changes that would be applied for each file:
 
 `black --diff {{path/to/file_or_directory}}`
 
-- Return the status without writing the files back:
+- Check the need of auto-formatting without altering the files:
 
 `black --check {{path/to/file_or_directory}}`