public com.google.protobuf.ByteString getUsageBytes() {
        java.lang.Object ref = usage_;
        if (ref instanceof String) {
          com.google.protobuf.ByteString b =
              com.google.protobuf.ByteString.copyFromUtf8((java.lang.String) ref);
          usage_ = b;
          return b;
        } else {
          return (com.google.protobuf.ByteString) ref;
        }
      }
<pre>
Optional. Usage of the file contents. Options are TRAIN|VALIDATION|TEST,
or UNASSIGNED (by default) for auto split.
</pre>

<code>string usage = 2 [(.google.api.field_behavior) = OPTIONAL];</code>

@return The bytes for usage.
java-translate/proto-google-cloud-translate-v3/src/main/java/com/google/cloud/translate/v3/DatasetInputConfig.java