Perform widget rendering, but do not print anything.

def _render_content(self, content, **settings):
        """
        Perform widget rendering, but do not print anything.
        """
        result = []
        bars = settings[self.SETTING_BARS]

        label_width = self.chart_measure(bars)
        if not settings[self.SETTING_BAR_WIDTH]:
            settings[self.SETTING_BAR_WIDTH] = TERMINAL_WIDTH - label_width - 3
        max_value = max(content)
        i = 0
        for bar in content:
            result.append(self._render_bar(bars[i], bar, max_value, label_width, **settings))
            i += 1
        return result