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: metrics.rs
    path of file: ./repos/polkadot/node/core/runtime-api/src
    
    the code of the file until where you have to start completion: // Copyright (C) Parity Technologies (UK) Ltd.
// This file is part of Polkadot.

// Polkadot is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Polkadot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the impl
    
	fn try_register(registry: &prometheus::Registry) -> Result<Self, prometheus::PrometheusError> {
		let metrics = MetricsInner {
			chain_api_requests: prometheus::register(
				prometheus::CounterVec::new(
					prometheus::Opts::new(
						"polkadot_parachain_runtime_api_requests_total",
						"Number of Runtime API requests served.",
					),
					&["success"],
				)?,
				registry,
			)?,
			make_runtime_api_request: prometheus::register(
				prometheus::Histogram::with_opts(prometheus::HistogramOpts::new(
					"polkadot_parachain_runtime_api_make_runtime_api_request",
					"Time spent within `runtime_api::make_runtime_api_request`",
				))?,
				registry,
			)?,
		};
		Ok(Metrics(Some(metrics)))
	}