Format the value of a metric value to a string

    :param val: number to be formatted
    :return: a string with the formatted value

def str_val(val):
    """
    Format the value of a metric value to a string

    :param val: number to be formatted
    :return: a string with the formatted value
    """
    str_val = val
    if val is None:
        str_val = "NA"
    elif type(val) == float:
        str_val = '%0.2f' % val
    else:
        str_val = str(val)
    return str_val