You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: span.rs
    path of file: ./repos/phaser/phaser/vendor/tracing/src
    
    the code of the file until where you have to start completion: //! Spans represent periods of time in which a program was executing in a
//! particular context.
//!
//! A span consists of [fields], user-defined key-value pairs of arbitrary data
//! that describe the context the span represents, and a set of fixed attributes
//! that describe all `tracing` spans and events. Attributes describing spans
/
    
    pub fn current() -> Span {
        dispatcher::get_default(|dispatch| {
            if let Some((id, meta)) = dispatch.current_span().into_inner() {
                let id = dispatch.clone_span(&id);
                Self {
                    inner: Some(Inner::new(id, dispatch)),
                    meta: Some(meta),
                }
            } else {
                Self::none()
            }
        })
    }