def get_choices(self):
        """
        Return a list of choices for source files found in configured layout
        template directories.
        """
        choices = []
        for label_prefix, templates_dir, template_name_prefix in \
                appsettings.LAYOUT_TEMPLATES:
            source_dir = os.path.join(templates_dir, template_name_prefix)
            # Walk directories, appending a choice for each source file.
            for local, dirs, files in os.walk(source_dir, followlinks=True):
                for source_file in files:
                    template_name = os.path.join(
                        template_name_prefix, source_file)
                    label = '%s: %s' % (label_prefix, source_file)
                    choices.append((template_name, label))
        return choices
Return a list of choices for source files found in configured layout
        template directories.