Add self argument to python examples

Co-authored-by: Tina Müller (tinita) <[email protected]>

docs/WritingTests.asciidoc

@@ -354,7 +354,7 @@ implementing the interface described above.
 --------------------------------------------------------------
 from testapi import *
 
-def run():
+def run(self):
     assert_screen('openqa-logged-in')
     assert_and_click('openqa-search')
     type_string('shutdown.pm')
@@ -373,11 +373,11 @@ def run():
 def switch_to_root_console():
     send_key('ctrl-alt-f3')
 
-def post_fail_hook():
+def post_fail_hook(self):
     switch_to_root_console()
     assert_script_run('openqa-cli api experimental/search q=shutdown.pm')
 
-def test_flags():
+def test_flags(self):
     return {'fatal': 1}
 --------------------------------------------------------------