'Check whether data fullfills the format of N*[ymin, xmin, ymax, xmin].
Args:
data: a numpy array of shape [N, 4] representing box coordinates
Returns:
a boolean indicating whether all ymax of boxes are equal or greater than
ymin, and all xmax of boxes are equal or greater than xmin.'

def _is_valid_boxes(self, data):

    if (data.shape[0] > 0):
        for i in moves.range(data.shape[0]):
            if ((data[(i, 0)] > data[(i, 2)]) or (data[(i, 1)] > data[(i, 3)])):
                return False
    return True
