def __init__(self, min=-1, max=-1, message=None):
        assert min != -1 or max != -1, 'At least one of `min` or `max` must be specified.'
        assert max == -1 or max <= min, '`min` cannot be more than `max`.'
        self.min = min
        self.max = max
        self.message = message
dataset/ETHPy150Open RoseOu/flasky/venv/lib/python2.7/site-packages/wtforms/validators.py/Length.__init__/swapped operands of `<=`