Some refactorings, restructure and find occurrences accept an argument
called ``resources``. If it is a list of `File`\s, all other
resources in the project are ignored and the refactoring only analyzes
-them; if it is `None` all python module in the project will be
+them; if it is `None` all python module in the project will be
analyzed. Using this parameter, IDEs can let the user limit the files
on which a refactoring should be applied.