public com.google.protobuf.ByteString getRevisionIdBytes() {
      java.lang.Object ref = revisionId_;
      if (ref instanceof String) {
        com.google.protobuf.ByteString b =
            com.google.protobuf.ByteString.copyFromUtf8((java.lang.String) ref);
        revisionId_ = b;
        return b;
      } else {
        return (com.google.protobuf.ByteString) ref;
      }
    }
<pre>
Optional. The revision of the workflow to retrieve. If the revision_id is
empty, the latest revision is retrieved.
The format is "000001-a4d", where the first six characters define
the zero-padded decimal revision number. They are followed by a hyphen and
three hexadecimal characters.
</pre>

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

@return The bytes for revisionId.
java-workflows/proto-google-cloud-workflows-v1/src/main/java/com/google/cloud/workflows/v1/GetWorkflowRequest.java