Panel objects, as returned by new_panel() above, are windows
with a stacking order. There's always a window associated with a
panel which determines the content, while the panel methods are
responsible for the window's depth in the panel stack.
Panel objects have the following methods:
Returns the panel above the current panel.
Returns the panel below the current panel.
Push the panel to the bottom of the stack.
Returns true if the panel is hidden (not visible), false otherwise.
Hide the panel. This does not delete the object, it just makes the
window on screen invisible.
Move the panel to the screen coordinates (y, x).
Change the window associated with the panel to the window win.
Set the panel's user pointer to obj. This is used to associate an
arbitrary piece of data with the panel, and can be any Python object.
Display the panel (which might have been hidden).
Push panel to the top of the stack.
Returns the user pointer for the panel. This might be any Python object.
Returns the window object associated with the panel.