code: def set_capstyle(self, cs):
      if cs in ("butt", "round", "projecting"):
          self._capstyle = cs
          self.ctx.set_line_cap(self._capd[cs])
      else:
          raise ValueError("Unrecognized cap style.  Found %s" % cs)
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  import gzip
  import sys
  import warnings
  import numpy
  from matplotlib.backend_bases import _Backend, FigureCanvasBase, FigureManagerBase, GraphicsContextBase, RendererBase
  from matplotlib.mathtext import MathTextParser
  from matplotlib.path import Path
  from matplotlib.transforms import Affine2D
  from matplotlib.font_manager import ttfFontProperty
label_desc: Use image node_id 4 for calling the GraphicsContextCairo obj's underlying member method code with example usage: obj.set_capstyle(cs) without return types