input: Write a python function to check if a given window is currently selected in a tkinter Listbox.
  assert is_window_selected(['Window1', 'Window2', 'Window3'], 'Window2') == True
  assert is_window_selected(['Window1', 'Window2', 'Window3'], 'Window4') == False
  assert is_window_selected([], 'Window1') == False
output: def is_window_selected(window_list, window_name):
      return window_name in window_list