class_docstr: an axis spine -- the line noting the data area boundaries
  
  Spines are the lines connecting the axis tick marks and noting the
  boundaries of the data area. They can be placed at arbitrary
  positions. See function:`~matplotlib.spines.Spine.set_position`
  for more information.
  
  The default position is ``('outward',0)``.
  
  Spines are subclasses of class:`~matplotlib.patches.Patch`, and
  inherit much of their behavior.
  
  Spines draw a line, a circle, or an arc depending if
  function:`~matplotlib.spines.Spine.set_patch_line`,
  function:`~matplotlib.spines.Spine.set_patch_circle`, or
  function:`~matplotlib.spines.Spine.set_patch_arc` has been called.
  Line-like is the default.
docstr: - *axes* : the Axes instance containing the spine
  - *spine_type* : a string specifying the spine type
  - *path* : the path instance used to draw the spine
  
  Valid kwargs are:
  %(Patch)s
code: def __init__(self, axes, spine_type, path, **kwargs):
      """
      - *axes* : the Axes instance containing the spine
      - *spine_type* : a string specifying the spine type
      - *path* : the path instance used to draw the spine
  
      Valid kwargs are:
      %(Patch)s
      """
      super(Spine, self).__init__(**kwargs)
      self.axes = axes
      self.set_figure(self.axes.figure)
      self.spine_type = spine_type
      self.set_facecolor("none")
      self.set_edgecolor(rcParams["axes.edgecolor"])
      self.set_linewidth(rcParams["axes.linewidth"])
      self.set_capstyle("projecting")
      self.axis = None
  
      self.set_zorder(2.5)
      self.set_transform(self.axes.transData)  # default transform
  
      self._bounds = None  # default bounds
      self._smart_bounds = False
  
      # Defer initial position determination. (Not much support for
      # non-rectangular axes is currently implemented, and this lets
      # them pass through the spines machinery without errors.)
      self._position = None
      if not isinstance(path, matplotlib.path.Path):
          raise ValueError(
              "'path' must be an instance of 'matplotlib.path.Path'"
          )
      self._path = path
  
      # To support drawing both linear and circular spines, this
      # class implements Patch behavior three ways. If
      # self._patch_type == 'line', behave like a mpatches.PathPatch
      # instance. If self._patch_type == 'circle', behave like a
      # mpatches.Ellipse instance. If self._patch_type == 'arc', behave like
      # a mpatches.Arc instance.
      self._patch_type = "line"
  
      # Behavior copied from mpatches.Ellipse:
      # Note: This cannot be calculated until this is added to an Axes
      self._patch_transform = mtransforms.IdentityTransform()
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  import matplotlib
  from matplotlib.artist import allow_rasterization
  from matplotlib import docstring
  import matplotlib.transforms
  import matplotlib.patches
  import matplotlib.path
  import numpy
  import warnings
label_desc: Use image node_id 2 to create a new Spine object from inherited base classes: mpatches with example: obj = Spine(axes, spine_type, path)