def trio( x ) :
    ''' Returns a new three-element list whose values are respectively the number of
        negative, zero, and positive values in list x
    '''

    pass


def flatten( d ) :
    ''' Returns a simple list whose elements are the elements of first row of dataset
        d, followed by the elements of the second row of d, and so.
    '''

    pass

if ( __name__ == '__main__' ) :
    import test_tf

    test_tf.test_trio()

    print()

    test_tf.test_flatten()