title: Add Method to Class AWS CDK
body: <p><a href="https://github.com/vennemp/cdk-nwfirewall" rel="nofollow noreferrer">https://github.com/vennemp/cdk-nwfirewall</a></p>
  <p>look at src/index.tx</p>
  <p>I have published an npm package for AWS CDK to deploy AWS Network Firewall.  It works great but I am currently expanding functionality and squashing bugs.   I am new to JS/TS so please excuse the spaghetti code.</p>
  <p>My Class is FirewallStack and in that it creates a vpc - line 62.</p>
  <p>When I create the FirewallStack, I want to be able to reference the subnets created in the vpc, like maybe even group them together - so if I want to launch a load balancer in the public subnets, I can just call the firewall stack and have amethod to grab the public subnets and pass that to my load balancer.</p>
  <p>I've looked at other example of people creating methods and it is not working.</p>
  <p>Have tried:</p>
  <pre><code>public listPublicSubnets (): FirewallStack {
     vpc.SubnetSelection(TYPE=PUBLIC)
  }
  </code></pre>
  <p>################</p>
  <pre><code>public listPublicSubnet(): FirewallStack {
      return publicSubnets
  }
  </code></pre>