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: version_number.rs
    path of file: ./repos/cargo-mobile/src/apple
    
    the code of the file until where you have to start completion: use crate::util::{VersionTriple, VersionTripleError};
use serde::{ser::Serializer, Serialize};
use std::fmt::{self, Debug, Display};
use thiserror::Error;

#[derive(Debug, Error)]
pub enum VersionNumberError {
    #[error("Failed to parse version triple.")]
    VersionTripleInvalid(#[from] VersionTripleError),
    #[error("Failed to parse extra version from {version:?}: {source}")]
    ExtraVersionInvalid {
        version: String,
        source: std::num::ParseIntError,
    },
}

#[derive(Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
pub struct VersionNumber {
    pub triple: VersionTriple,
    pub extra: Option<Vec<u32>>,
}

impl Display for VersionNumber {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt
    
    pub fn from_str(v: &str) -> Result<Self, VersionNumberError> {
        match v.split(".").count() {
            1 | 2 | 3 => {
                let triple = VersionTriple::from_str(v)?;
                Ok(Self {
                    triple,
                    extra: None,
                })
            }
            // Even when splitting a string that does not contain the delimeter, we should always get at least 1 split
            // (the full string, which could be the empty string)
            0 => unreachable!(),
            _ => {
                let mut s = v.split(".");
                let triple = VersionTriple::from_split(&mut s, v)?;
                let extra = Some(
                    s.map(|s| {
                        s.parse()
                            .map_err(|source| VersionNumberError::ExtraVersionInvalid {
                                version: v.to_owned(),
                                source,
                            })
                    })
                    .collect::<Result<Vec<_>, _>>()?,
                );
                Ok(Self { triple, extra })
            }
        }
    }