<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def dump_age(age=None):
 """Formats the duration as a base-10 integer. :param age: should be an integer number of seconds, a :class:`datetime.timedelta` object, or, if the age is unknown, `None` (default). """

    if age is None:
        return
    if isinstance(age, timedelta):
        # do the equivalent of Python 2.7's timedelta.total_seconds(),
        # but disregarding fractional seconds
        age = age.seconds + (age.days * 24 * 3600)

    age = int(age)
    if age < 0:
        raise ValueError("age cannot be negative")

    return str(age)