Function pretty 

pub fn pretty<C, S>(
    config: &C,
) -> (Layer<S, Pretty, Format<Pretty>>, LevelFilter)
where
    C: TracingConfig,
    for<'a> S: Subscriber + LookupSpan<'a>,

Create a Pretty format layer configured from the given TracingConfig.

Example

let config = TestAll;
let (layer, level_filter) = pretty(&config);
let layer = layer.with_filter(level_filter);
let _unused = set_default(vec![layer.boxed()]);
info!("info level");