def METHOD_NAME(self):
    """Write a single orphan residue using MMCIFIO."""
    struct1 = self.structure
    residue1 = list(struct1.get_residues())[0]
    residue1.parent = None  # detach residue
    # Write full model to temp file
    self.io.set_structure(residue1)
    filenumber, filename = tempfile.mkstemp()
    os.close(filenumber)
    try:
        self.io.save(filename)
        struct2 = self.mmcif_parser.get_structure("1a8o", filename)
        nresidues = len(list(struct2.get_residues()))
        self.assertEqual(nresidues, 1)
        # Assert chain is default: "A"
        chain_id = [c.id for c in struct2.get_chains()][0]
        self.assertEqual(chain_id, "A")
    finally:
        os.remove(filename)