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: requirement.rs
    path of file: ./repos/vector/lib/vector-core/src/schema
    
    the code of the file until where you have to start completion: use std::collections::{BTreeMap, BTreeSet};

use lookup::OwnedTargetPath;
use vrl::value::Kind;

use crate::config::LogNamespace;

use super::Definition;

/// The input schema for a given component.
///
/// This sch
    
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::MeaningMissing { identifier } => {
                write!(f, "missing semantic meaning: {identifier}")
            }
            Self::MeaningKind {
                identifier,
                want,
                got,
            } => write!(
                f,
                "invalid semantic meaning: {identifier} (expected {want}, got {got})"
            ),
            Self::MeaningDuplicate { identifier, paths } => write!(
                f,
                "semantic meaning {} pointing to multiple fields: {}",
                identifier,
                paths
                    .iter()
                    .map(ToString::to_string)
                    .collect::<Vec<_>>()
                    .join(", ")
            ),
        }
    }