code: @BetaApi
    public final Operation addInstanceTargetPool(
        ProjectRegionTargetPoolName targetPool,
        TargetPoolsAddInstanceRequest targetPoolsAddInstanceRequestResource) {
  
      AddInstanceTargetPoolHttpRequest request =
          AddInstanceTargetPoolHttpRequest.newBuilder()
              .setTargetPool(targetPool == null ? null : targetPool.toString())
              .setTargetPoolsAddInstanceRequestResource(targetPoolsAddInstanceRequestResource)
              .build();
      return addInstanceTargetPool(request);
    }
docs: Adds an instance to a target pool.
  
  <p>Sample code:
  
  <pre><code>
  try (TargetPoolClient targetPoolClient = TargetPoolClient.create()) {
  ProjectRegionTargetPoolName targetPool = ProjectRegionTargetPoolName.of("[PROJECT]", "[REGION]", "[TARGET_POOL]");
  TargetPoolsAddInstanceRequest targetPoolsAddInstanceRequestResource = TargetPoolsAddInstanceRequest.newBuilder().build();
  Operation response = targetPoolClient.addInstanceTargetPool(targetPool, targetPoolsAddInstanceRequestResource);
  }
  </code></pre>
  
  @param targetPool Name of the TargetPool resource to add instances to.
  @param targetPoolsAddInstanceRequestResource
  @throws com.google.api.gax.rpc.ApiException if the remote call fails