start_activity not working

Could you help me? I’m really new into Ruby and Appium and struggled some time with “activity”. methods, but without success.

How to use start_activity or current_activity it in Ruby? I have code (based on some tutorials):

config.before(:all) do
@driver = Appium::Driver.new(caps)
@driver.start_driver
end

but when I write:

@driver.current_activity
error is - method not found.

When I navigate to this class (Appium::Driver) in IntelliJ - it tells me about files: driver.rb or android/dynamic.rb located in:

C:/Programy/Ruby193/lib/ruby/gems/1.9.1/gems/appium_lib-3.0.3/lib/appium_lib/

When I search in files content in this location for string start_activity - I can’t found any file with this method. Is it method deprecated? Or I do something wrong? The same problem is with current_activity.