The attribute to set or unset is specified by attribute. This
can be one of the standard attribute names G_MENU_ATTRIBUTE_LABEL,
G_MENU_ATTRIBUTE_ACTION, G_MENU_ATTRIBUTE_TARGET, or a custom
attribute name.
Attribute names are restricted to lowercase characters, numbers
and '-'. Furthermore, the names must begin with a lowercase character,
must not end with a '-', and must not contain consecutive dashes.
must consist only of lowercase
ASCII characters, digits and '-'.
If value is non-NULL then it is used as the new value for the
attribute. If value is NULL then the attribute is unset. If
the valueglib.Variant is floating, it is consumed.
Sets or unsets an attribute on menu_item.
The attribute to set or unset is specified by attribute. This can be one of the standard attribute names G_MENU_ATTRIBUTE_LABEL, G_MENU_ATTRIBUTE_ACTION, G_MENU_ATTRIBUTE_TARGET, or a custom attribute name. Attribute names are restricted to lowercase characters, numbers and '-'. Furthermore, the names must begin with a lowercase character, must not end with a '-', and must not contain consecutive dashes.
must consist only of lowercase ASCII characters, digits and '-'.
If value is non-NULL then it is used as the new value for the attribute. If value is NULL then the attribute is unset. If the value glib.Variant is floating, it is consumed.
See also Menu.itemSetAttribute for a more convenient way to do the same.