code: protected static SiftsChainToUniprotMapping build() throws IOException {
  		SiftsChainToUniprotMapping sifts = new SiftsChainToUniprotMapping();
  		BufferedReader br = new BufferedReader(new FileReader(DEFAULT_FILE));
  		String line = "";
  		while ((line = br.readLine()) != null) {
  			if (line.isEmpty() || line.startsWith("#") || line.startsWith("PDB")) continue;
  			String[] parts = line.split("\t");
  			String pdbId = parts[0];
  			String chainId = parts[1];
  			String uniProtId = parts[2];
  			String seqresStart = parts[3];
  			String seqresEnd = parts[4];
  			String pdbStart = parts[5];
  			String pdbEnd = parts[6];
  			String uniprotStart = parts[7];
  			String uniprotEnd = parts[8];
  			SiftsChainEntry entry = new SiftsChainEntry(pdbId, chainId, uniProtId, seqresStart, seqresEnd,
  					pdbStart, pdbEnd, uniprotStart, uniprotEnd);
  			sifts.byChainId.put(pdbId + "." + chainId, entry);
  			sifts.byUniProtId.put(uniProtId, entry);
  		}
  		br.close();
  		return sifts;
  	}
docs: Builds the mapping by reading SIFTS the tsv file set in {@link #DEFAULT_FILE} variable.
  @return
  @throws IOException