Python doctest

I've recently picked up Python again, and a neat feature that I ran across by chance is the doctest module.
It tests if the example in your docstrings actually do what you claim! ¹

Let's say we have this neat is_leap_year function with a few examples.
Note that the examples are all prefixed with >>> (That's from the interactive prompt.)

def _is_leap_year(year: int) -> bool:
    """Determines if a year is a leap year.
    >>> _is_leap_year(2020)
    True
    >>> _is_leap_year(2100)
    False
    >>> _is_leap_year(2000)
    True
    """
    return divides(400, year) or (divides(4, year) and not divides(100, year))

if __name__ == '__main__':
    import doctest
    doctest.testmod()

Calling doctest.testmod looks at all the examples in this module, runs the code and compares the result.