<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def render_icon(icon, **kwargs):
 """ Render a Bootstrap glyphicon icon """

    attrs = {
        "class": add_css_class(
            "glyphicon glyphicon-{icon}".format(icon=icon),
            kwargs.get("extra_classes", ""),
        )
    }
    title = kwargs.get("title")
    if title:
        attrs["title"] = title
    return render_tag("span", attrs=attrs)