'nth_coord = along which coordinate value varies.
nth_coord = 0 ->  x axis, nth_coord = 1 -> y axis'

def __init__(self, grid_helper, nth_coord, value, axis_direction=None):

    super(FloatingAxisArtistHelper, self).__init__(nth_coord, value)
    self.value = value
    self.grid_helper = grid_helper
    self._extremes = (None, None)
    self._get_line_path = None
    self._line_num_points = 100
