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: hyper.rs
    path of file: ./repos/multipart/src/server
    
    the code of the file until where you have to start completion: // Copyright 2016 `multipart` Crate Developers
//
// Licensed under the Apache License, Vers
    
    fn multipart_boundary(&self) -> Option<&str> {
        if self.method != Method::Post {
            return None;
        }

        self.headers.get::<ContentType>().and_then(|ct| {
            let ContentType(ref mime) = *ct;
            let params = match *mime {
                Mime(TopLevel::Multipart, SubLevel::FormData, ref params) => params,
                _ => return None,
            };

            params.iter().find(|&&(ref name, _)|
                match *name {
                    Attr::Boundary => true,
                    _ => false,
                }
            ).and_then(|&(_, ref val)|
                match *val {
                    Value::Ext(ref val) => Some(&**val),
                    _ => None,
                }
            )
        })
    }