Sphinx/create_identifiers: use `not in` not `not _ in`

Utilities/Sphinx/create_identifiers.py

@@ -38,7 +38,7 @@ for line in lines:
 
   for domain_object_string, domain_object_type in mapping:
     if "<keyword name=\"" + domain_object_string + "\"" in line:
-      if not "id=\"" in line and not "#index-" in line:
+      if "id=\"" not in line and "#index-" not in line:
         prefix = "<keyword name=\"" + domain_object_string + "\" "
         part1, part2 = line.split(prefix)
         head, tail = part2.split("#" + domain_object_type + ":")