@register.filter
def showextrawhitespace(value):
    value = extraWhitespace.sub(r'<span class="ew">\1</span>', value)
    return value.replace("\t", '<span class="tb">\t</span>')
Marks up any extra whitespace in the specified text.
dataset/ETHPy150Open reviewboard/reviewboard/reviewboard/diffviewer/templatetags/difftags.py/showextrawhitespace