This is a static method which creates a new
GtkExpander instance using label
as the text of the label. If characters in label are preceded by an
underscore, they are underlined. If you need a literal underscore character
in a label, use '__' (two underscores). The first underlined character
represents a keyboard accelerator called a mnemonic. Pressing Alt with that
key activates the button. If label is Null the expander
will have no label.
This method is a shortcut, you can achieve the same results by creating a
new GtkExpander instance with a label containing an
underscore and then calling the set_use_underline()
This method must be called statically.