Retrieves the metadata value for key.
If expected_type is non-null, any non-null value returned from this function will match expected_type.
the metadata key
a #GVariantType or null
a non-floating #GVariant which should be released with glib.variant.Variant.unref; otherwise null.
Retrieves the metadata value for key.
If expected_type is non-null, any non-null value returned from this function will match expected_type.