code: function(fromNumAndIns, toNumAndIns, ss) {
      // FIXME: when the chain numbers are completely ordered, perform binary 
      // search to identify range of residues to assign secondary structure to.
      var from = rnumInsCodeHash(fromNumAndIns[0], fromNumAndIns[1]);
      var to = rnumInsCodeHash(toNumAndIns[0], toNumAndIns[1]);
      for (var i = 1; i < this._residues.length-1; ++i) {
        var res = this._residues[i];
        // FIXME: we currently don't set the secondary structure of the last 
        // residue of helices and sheets. that takes care of better transitions 
        // between coils and helices. ideally, this should be done in the 
        // cartoon renderer, NOT in this function.
        var combined = rnumInsCodeHash(res.num(), res.insCode());
        if (combined <  from || combined >= to) {
          continue;
        }
        res.setSS(ss);
      }
    }
docs: assigns secondary structure to residues in range from_num to to_num.