@java.lang.Override
  public com.google.protobuf.ByteString getTpuTopologyBytes() {
    java.lang.Object ref = tpuTopology_;
    if (ref instanceof java.lang.String) {
      com.google.protobuf.ByteString b =
          com.google.protobuf.ByteString.copyFromUtf8((java.lang.String) ref);
      tpuTopology_ = b;
      return b;
    } else {
      return (com.google.protobuf.ByteString) ref;
    }
  }
<pre>
Immutable. The topology of the TPUs. Corresponds to the TPU topologies
available from GKE. (Example: tpu_topology: "2x2x1").
</pre>

<code>string tpu_topology = 4 [(.google.api.field_behavior) = IMMUTABLE];</code>

@return The bytes for tpuTopology.
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/MachineSpec.java