code: function sheet_to_rtf(ws) {
  		var o = ["{\\rtf1\\ansi"];
  		var r = safe_decode_range(ws['!ref']), cell;
  		var dense = Array.isArray(ws);
  		for(var R = r.s.r; R <= r.e.r; ++R) {
  			o.push("\\trowd\\trautofit1");
  			for(var C = r.s.c; C <= r.e.c; ++C) o.push("\\cellx" + (C+1));
  			o.push("\\pard\\intbl");
  			for(C = r.s.c; C <= r.e.c; ++C) {
  				var coord = encode_cell({r:R,c:C});
  				cell = dense ? (ws[R]||[])[C]: ws[coord];
  				if(!cell || cell.v == null && (!cell.f || cell.F)) continue;
  				o.push(" " + (cell.w || (format_cell(cell), cell.w)));
  				o.push("\\cell");
  			}
  			o.push("\\pard\\intbl\\row");
  		}
  		return o.join("") + "}";
  	}
docs: /* TODO: this is a stub