Gets a header field on this.
The caller is responsible for checking the type of the returned [type@GLib.Variant] matches what is expected.
| this |
a D-Bus message |
| header_field |
a 8-bit unsigned integer (typically a value from the [enum@Gio.DBusMessageHeaderField] enumeration) |
|
A [type@GLib.Variant] with the value, or `NULL` if the header was not found |