'Return a cropped grid response.'

def crop(self, bbox):

    (minchar, minrow, maxchar, maxrow) = [(v / self.scale) for v in bbox]
    (keys, data) = (self.content['keys'], self.content.get('data', None))
    grid = [row[minchar:maxchar] for row in self.content['grid'][minrow:maxrow]]
    cropped = dict(keys=keys, data=data, grid=grid)
    return SaveableResponse(cropped, self.scale)
