code: def get_browser_controller(browser=None):
      ''' Return a browser controller.
  
      Args:
          browser (str or None) : browser name, or ``None`` (default: ``None``)
              If passed the string ``'none'``, a dummy web browser controller
              is returned
  
              Otherwise, use the value to select an appropriate controller using
              the ``webbrowser`` standard library module. In the value is
              ``None`` then a system default is used.
  
      .. note::
          If the environment variable ``BOKEH_BROWSER`` is set, it will take
          precedence.
  
      Returns:
          controller : a web browser controller
  
      '''
      browser = settings.browser(browser)
  
      if browser is not None:
          if browser == 'none':
              controller = DummyWebBrowser()
          else:
              controller = webbrowser.get(browser)
      else:
          controller = webbrowser
  
      return controllef get_browser_controller(browser=None):
      ''' Return a browser controller.
  
      Args:
          browser (str or None) : browser name, or ``None`` (default: ``None``)
              If passed the string ``'none'``, a dummy web browser controller
              is returned
  
              Otherwise, use the value to select an appropriate controller using
              the ``webbrowser`` standard library module. In the value is
              ``None`` then a system default is used.
  
      .. note::
          If the environment variable ``BOKEH_BROWSER`` is set, it will take
          precedence.
  
      Returns:
          controller : a web browser controller
  
      '''
      browser = settings.browser(browser)
  
      if browser is not None:
          if browser == 'none':
              controller = DummyWebBrowser()
          else:
              controller = webbrowser.get(browser)
      else:
          controller = webbrowser
  
      return controller
docs: Return a browser controller.
  
      Args:
          browser (str or None) : browser name, or ``None`` (default: ``None``)
              If passed the string ``'none'``, a dummy web browser controller
              is returned
  
              Otherwise, use the value to select an appropriate controller using
              the ``webbrowser`` standard library module. In the value is
              ``None`` then a system default is used.
  
      .. note::
          If the environment variable ``BOKEH_BROWSER`` is set, it will take
          precedence.
  
      Returns:
          controller : a web browser controller