public function set_theme_suite_to_include_core_features($themetoset) {
        // If no value passed to --add-core-features-to-theme or ALL is passed, then set core features for all themes.
        if (!empty($themetoset)) {
            if (is_number($themetoset) || is_bool($themetoset) || (self::ALL_THEMES_TO_RUN === strtoupper($themetoset))) {
                $this->themesuitewithallfeatures = self::ALL_THEMES_TO_RUN;
            } else {
                $this->themesuitewithallfeatures = explode(',', $themetoset);
                $this->themesuitewithallfeatures = array_map('trim', $this->themesuitewithallfeatures);
            }
        }
    }