getSpiros() {
    let spiros = Array();

    for (var i = 0; i < this.rings.length; i++) {
      if (this.rings[i].isSpiro) {
        spiros.push(this.rings[i]);
      }
    }

    return spiros;
  }
Returns an array containing all spiros associated with this molecule.

@returns {Ring[]} An array containing all spiros associated with this molecule.