code: def load_extra_vi_page_navigation_bindings():
      
      registry = ConditionalRegistry(Registry(), ViMode())
      handle = registry.add_binding
  
      handle(Keys.ControlF)(scroll_forward)
      handle(Keys.ControlB)(scroll_backward)
      handle(Keys.ControlD)(scroll_half_page_down)
      handle(Keys.ControlU)(scroll_half_page_up)
      handle(Keys.ControlE)(scroll_one_line_down)
      handle(Keys.ControlY)(scroll_one_line_up)
      handle(Keys.PageDown)(scroll_page_down)
      handle(Keys.PageUp)(scroll_page_up)
  
      return registry
docs: Key bindings, for scrolling up and down through pages.
      This are separate bindings, because GNU readline doesn't have them.