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: set the spine to be arc-like
code: def set_patch_arc(self, center, radius, theta1, theta2):
      """set the spine to be arc-like"""
      self._patch_type = "arc"
      self._center = center
      self._width = radius * 2
      self._height = radius * 2
      self._theta1 = theta1
      self._theta2 = theta2
      self._path = mpath.Path.arc(theta1, theta2)
      # arc drawn on axes transform
      self.set_transform(self.axes.transAxes)
      self.stale = True
  
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 5 for calling the Spine obj's underlying member method code with example usage: obj.set_patch_arc(center, radius, theta1, theta2) without return types