def getCSS(self):
        """ Returns the css style to be used for the current template.
            If the selected template is 'default.pt', this method will
            return the content from 'default.css'. If no css file found
            for the current template, returns empty string
        """
        template = self.request.get('template', self._DEFAULT_TEMPLATE)
        content = ''
        if template.find(':') >= 0:
            prefix, template = template.split(':')
            resource = queryResourceDirectory(
                self._TEMPLATES_ADDON_DIR, prefix)
            css = '{0}.css'.format(template[:-3])
            if css in resource.listDirectory():
                content = resource.readFile(css)
        else:
            this_dir = os.path.dirname(os.path.abspath(__file__))
            templates_dir = os.path.join(this_dir, self._TEMPLATES_DIR)
            path = '%s/%s.css' % (templates_dir, template[:-3])
            with open(path, 'r') as content_file:
                content = content_file.read()
        return content
Returns the css style to be used for the current template.
            If the selected template is 'default.pt', this method will
            return the content from 'default.css'. If no css file found
            for the current template, returns empty string