code: def _wait_for_js(self):
      
  
      # No Selenium browser available, so return without doing anything
      if not hasattr(self, 'browser'):
          return
  
      # pylint: disable=protected-access
      # Wait for JavaScript variables to be defined
      if hasattr(self, '_js_vars') and self._js_vars:
          EmptyPromise(
              lambda: _are_js_vars_defined(self.browser, self._js_vars),
              u"JavaScript variables defined: {0}".format(", ".join(self._js_vars))
          ).fulfill()
  
      # Wait for RequireJS dependencies to load
      if hasattr(self, '_requirejs_deps') and self._requirejs_deps:
          EmptyPromise(
              lambda: _are_requirejs_deps_loaded(self.browser, self._requirejs_deps),
              u"RequireJS dependencies loaded: {0}".format(", ".join(self._requirejs_deps)),
              try_limit=5
          ).fulfill()
docs: Class method added by the decorators to allow
      decorated classes to manually re-check JavaScript
      dependencies.
  
      Expect that `self` is a class that:
      1) Has been decorated with either `js_defined` or `requirejs`
      2) Has a `browser` property
  
      If either (1) or (2) is not satisfied, then do nothing.