def METHOD_NAME(self):
    """Parse a multi-chain structure by ATOM entries.
    Reference:
    http://www.rcsb.org/pdb/files/fasta.txt?structureIdList=2BEG
    """
    chains = list(SeqIO.parse("PDB/2BEG." + extension, parser))
    self.assertEqual(len(chains), 5)
    actual_seq = "LVFFAEDVGSNKGAIIGLMVGGVVIA"
    for chain, chn_id in zip(chains, "ABCDE"):
        self.assertEqual(chain.id, "2BEG:" + chn_id)
        self.assertEqual(chain.annotations["chain"], chn_id)
        self.assertEqual(chain.annotations["model"], 0)
        self.assertEqual(chain.seq, actual_seq)
    with warnings.catch_warnings():
        warnings.simplefilter("ignore", PDBConstructionWarning)
        chains = list(SeqIO.parse("PDB/2XHE." + extension, parser))
    actual_seq = (
        "DRLSRLRQMAAENQXXXXXXXXXXXXXXXXXXXXXXXPEPFMADFFNRVK"
        "RIRDNIEDIEQAIEQVAQLHTESLVAVSKEDRDRLNEKLQDTMARISALG"
        "NKIRADLKQIEKENKRAQQEGTFEDGTVSTDLRIRQSQHSSLSRKFVKVM"
        "TRYNDVQAENKRRYGENVARQCRVVEPSLSDDAIQKVIEHGXXXXXXXXX"
        "XXXXXXXXNEIRDRHKDIQQLERSLLELHEMFTDMSTLVASQGEMIDRIE"
        "FSVEQSHNYV"
    )
    self.assertEqual(chains[1].seq, actual_seq)