Document run_args limitation on Python Modules.

Arguments sent from Perl to Python can't be used (due to blessed
references not properly translated to Python into usable objects).

A note of caution is added to warn against using any argument in
the `run` function and updated examples.

docs/WritingTests.asciidoc

@@ -65,7 +65,7 @@ And here is an example in Python:
 -------------------------------------------------------------------
 from testapi import *
 
-def run():
+def run(*_):
     # write in this block the code for your test.
 -------------------------------------------------------------------
 
@@ -76,7 +76,7 @@ _Please note that the subroutine marked with `*1` are optional._
 [source,python]
 -------------------------------------------------------------------
 # Written in type-hinted python to indicate explicitly return types
-def run(): -> None
+def run(*_):
 def test_flags(): -> dict # *1
 def post_fail_hook(): -> None # *1
 def pre_run_hook(): -> None # *1
@@ -222,7 +222,7 @@ from testapi import *
 
 # [...] omitted for brevity
 
-def run():
+def run(*_):
     perl.require('x11utils')
 
     # Start vncviewer - notice the named arguments passed as positional arguments
@@ -235,6 +235,11 @@ def run():
     # [...] omitted for brevity
 -------------------------------------------------------------------
 
+Additionally, the `run` method in Python is not able to handle any argument
+passed. Due to how `Inline::Python` handles arguments passing between Perl <->
+Python, references to complex Perl objects do not reach python properly and
+they can't be used.
+
 === Example Perl test modules
 [id="testmodule_perl_examples"]
 
@@ -354,7 +359,7 @@ implementing the interface described above.
 --------------------------------------------------------------
 from testapi import *
 
-def run(self):
+def run(*_):
     assert_screen('openqa-logged-in')
     assert_and_click('openqa-search')
     type_string('shutdown.pm')