docstr: nth_coord = along which coordinate value varies.
   nth_coord = 0 ->  x axis, nth_coord = 1 -> y axis
code: def __init__(
      self, grid_helper, nth_coord, value, axis_direction=None
  ):
      """
      nth_coord = along which coordinate value varies.
       nth_coord = 0 ->  x axis, nth_coord = 1 -> y axis
      """
  
      super(FloatingAxisArtistHelper, self).__init__(
          nth_coord,
          value,
      )
      self.value = value
      self.grid_helper = grid_helper
      self._extremes = None, None
  
      self._get_line_path = None  # a method that returns a Path.
      self._line_num_points = 100
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  from six.moves import zip
  from itertools import chain
  from .grid_finder import GridFinder
  from .axislines import AxisArtistHelper, GridHelperBase
  from .axis_artist import AxisArtist
  from matplotlib.transforms import Affine2D, IdentityTransform
  import numpy
  from matplotlib.path import Path
label_desc: Use image node_id 1 to create a new FloatingAxisArtistHelper object from inherited base classes: AxisArtistHelper with example: obj = FloatingAxisArtistHelper(grid_helper, nth_coord, value, axis_direction)