code: def send_figure(self, fig, caption=''):
          
          if not self.is_token_set:
              raise ValueError('TelepythClient: Access token is not set!')
  
          figure = BytesIO()
          fig.savefig(figure, format='png')
          figure.seek(0)
  
          parts = [ContentDisposition('caption', caption),
                   ContentDisposition('figure', figure, filename="figure.png",
                                      content_type='image/png')]
  
          form = MultipartFormData(*parts)
          content_type = 'multipart/form-data; boundary=%s' % form.boundary
  
          url = self.base_url + self.access_token
          req = Request(url, method='POST')
          req.add_header('Content-Type', content_type)
          req.add_header('User-Agent', __user_agent__ + '/' + __version__)
          req.data = form().read()
  
          res = urlopen(req)
  
          return res.getcode()
docs: Render matplotlib figure into temporary bytes buffer and then send
          it to telegram user.
  
          :param fig: matplotlib figure object.
          :param caption: text caption of picture.
          :return: status code on error.