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: d_ir.rs
    path of file: ./repos/chiselstrike/chiselc/src/tools/analysis
    
    the code of the file until where you have to start completion: // SPDX-FileCopyrightText: Â© 2022 ChiselStrike <info@chiselstrike.com>

// This module is not used for *now*. Ultimately, Dir will be used to bring more features to the
// filter syntax, but it was there already, it'll stick around for when we need it.
#![allow(dead_code)]
///! This module contains the code for the D_IR described in [this paper](https://www.cse.iitb.ac.in/~venkateshek/p1781-emani.pdf). This 
    
    fn build_region(&mut self, region: &Region, ctx: &mut GraphContext) -> Result<EnrichedRegion> {
        let region = match region {
            Region::BasicBlock(_) => self.build_basic_block(region, ctx),
            Region::Seq(_) => self.build_seq_region(region, ctx)?,
            Region::Cond(_) => self.build_cond_region(region, ctx)?,
            Region::Loop(_) => bail!("loops are not supported!"),
        };

        Ok(region)
    }