#! /usr/bin/python3
#
# This example shows some built in unit tests for functions, alone with
# docstring examples.

def square(x):
    """ 
    Returns x times itself.
    >>> square(2)
    4
    >>> square(4)
    16
    >>> square(333)
    110889
    """
    return x*x

if __name__ == "__main__":
    """
    This is how doctest would be used in a module.
    """
    import doctest
    doctest.testmod()