Function omnisensor::dbus_helpers::props::prop_get_optional_from

pub fn prop_get_optional_from<'a, I, T>(
    map: &'a PropMap,
    key: &str
) -> Result<Option<T>, Box<dyn Error>>where
    T: TryFrom<&'a I, Error = Box<dyn Error>>,
    I: 'static,

Like prop_get_optional(), but converts to a more specific type T via an intermediate type I using TryFrom.

For example, an enum represented on dbus as a string can be easily converted to its internal representation as long as the internal enum implements TryFrom<&String>. (I is most often String, but does not have to be.)