code: def _remote_browser_class(env_vars, tags=None):
      
      if tags is None:
          tags = []
  
      # Interpret the environment variables, raising an exception if they're
      # invalid
      envs = _required_envs(env_vars)
      envs.update(_optional_envs())
  
      # Turn the environment variables into a dictionary of desired capabilities
      caps = _capabilities_dict(envs, tags)
  
      if 'accessKey' in caps:
          LOGGER.info(u"Using SauceLabs: %s %s %s", caps['platform'], caps['browserName'], caps['version'])
      else:
          LOGGER.info(u"Using Remote Browser: %s", caps['browserName'])
  
      # Create and return a new Browser
      # We assume that the WebDriver end-point is running locally (e.g. using
      # SauceConnect)
      url = u"http://{0}:{1}/wd/hub".format(
          envs['SELENIUM_HOST'], envs['SELENIUM_PORT'])
  
      browser_args = []
      browser_kwargs = {
          'command_executor': url,
          'desired_capabilities': caps,
      }
      if caps['browserName'] == 'firefox':
          browser_kwargs['browser_profile'] = _firefox_profile()
  
      return webdriver.Remote, browser_args, browser_kwargs
docs: Returns class, kwargs, and args needed to instantiate the remote browser.