code: def set_joinstyle(self, js):
      self.ctx.set_line_join(
          _api.check_getitem(self._joind, joinstyle=js)
      )
      self._joinstyle = js
  
imports: import functools
  import gzip
  import math
  import numpy
  from ..None import _api, cbook, font_manager
  from matplotlib.backend_bases import _Backend, FigureCanvasBase, FigureManagerBase, GraphicsContextBase, RendererBase
  from matplotlib.font_manager import ttfFontProperty
  from matplotlib.path import Path
  from matplotlib.transforms import Affine2D
label_desc: Use image node_id 12 for calling the GraphicsContextCairo obj's underlying member method code with example usage: obj.set_joinstyle(js) without return types