docs: function Commitment(opts) {
    $.checkArgument(opts.publicKeys && opts.publicKeys.length === 2, 'Must provide exactly two public keys');
    Transaction.call(this, opts.transaction);
  
    this.network = opts.network || 'livenet';
    this.publicKeys = opts.publicKeys;
    this.outscript = Script.buildMultisigOut(this.publicKeys, 2);
    this.address = this.outscript.toScriptHashOut().toAddress();
    if (!this.outputs.length) {
      this.change(this.address);
    }
  
    Object.defineProperty(this, 'amount', {
      configurable: false,
      get: function() {
        return this.inputAmount;
      }
    });
  }