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: mod.rs
    path of file: ./repos/delta-rs/crates/core/src/data_catalog/client
    
    the code of the file until where you have to start completion: //! Generic utilities reqwest based Catalog implementations

pub mod backoff;
#[cfg(test)]
pub mod mock_server;
#[allow(unused)]
pub mod pagination;
pub mod retry;
pub mod token;

use reqwest::header::{HeaderMap, HeaderValue};
use reqwest::{Client, ClientBuilder, Proxy};
use std::time::Duration;

fn map_cl
    
    pub(crate) fn client(&self) -> super::DataCatalogResult<Client> {
        let mut builder = ClientBuilder::new();

        match &self.user_agent {
            Some(user_agent) => builder = builder.user_agent(user_agent),
            None => builder = builder.user_agent(DEFAULT_USER_AGENT),
        }

        if let Some(headers) = &self.default_headers {
            builder = builder.default_headers(headers.clone())
        }

        if let Some(proxy) = &self.proxy_url {
            let proxy = Proxy::all(proxy).map_err(map_client_error)?;
            builder = builder.proxy(proxy);
        }

        if let Some(timeout) = self.timeout {
            builder = builder.timeout(timeout)
        }

        if let Some(timeout) = self.connect_timeout {
            builder = builder.connect_timeout(timeout)
        }

        if let Some(timeout) = self.pool_idle_timeout {
            builder = builder.pool_idle_timeout(timeout)
        }

        if let Some(max) = self.pool_max_idle_per_host {
            builder = builder.pool_max_idle_per_host(max)
        }

        if let Some(interval) = self.http2_keep_alive_interval {
            builder = builder.http2_keep_alive_interval(interval)
        }

        if let Some(interval) = self.http2_keep_alive_timeout {
            builder = builder.http2_keep_alive_timeout(interval)
        }

        if self.http2_keep_alive_while_idle {
            builder = builder.http2_keep_alive_while_idle(true)
        }

        if self.http1_only {
            builder = builder.http1_only()
        }

        if self.http2_only {
            builder = builder.http2_prior_knowledge()
        }

        if self.allow_insecure {
            builder = builder.danger_accept_invalid_certs(self.allow_insecure)
        }

        builder
            .https_only(!self.allow_http)
            .build()
            .map_err(map_client_error)
    }