def add_css_tag(token, modification):
    """Returns a token wrapped with the corresponding css tag."""

    if modification == 'replace':
        token = '<span class=\"delta-replace\">' + token + '</span>'
    elif modification == 'delete':
        token = '<span class=\"delta-delete\">' + token + '</span>'
    elif modification == 'append':
        token = '<span class=\"delta-insert\">' + token + '</span>'
    elif modification == 'punctuation':
        token = token[:-1] + '<span class=\"delta-insert\">' + token[-1] + '</span>'
    elif modification == 'input_delete':
        token = '<span class=\"delta-input-delete\">' + token + '</span>'
    elif modification == 'input_replace':
        token = '<span class=\"delta-input-replace\">' + token + '</span>'
    return token