public com.google.protobuf.ByteString getApiVersionBytes() {
      java.lang.Object ref = apiVersion_;
      if (ref instanceof String) {
        com.google.protobuf.ByteString b =
            com.google.protobuf.ByteString.copyFromUtf8((java.lang.String) ref);
        apiVersion_ = b;
        return b;
      } else {
        return (com.google.protobuf.ByteString) ref;
      }
    }
<pre>
API version used to start the operation.
</pre>

<code>string api_version = 5;</code>

@return The bytes for apiVersion.
java-workflows/proto-google-cloud-workflows-v1beta/src/main/java/com/google/cloud/workflows/v1beta/OperationMetadata.java