code: public com.google.protobuf.ByteString
        getFilenameBytes() {
      java.lang.Object ref = filename_;
      if (ref instanceof java.lang.String) {
        com.google.protobuf.ByteString b = 
            com.google.protobuf.ByteString.copyFromUtf8(
                (java.lang.String) ref);
        filename_ = b;
        return b;
      } else {
        return (com.google.protobuf.ByteString) ref;
      }
    }
docs: <pre>
  The filename within an assets directory. Note: does not include the path
  prefix, i.e. directories. For an asset at /tmp/path/vocab.txt, the filename
  would be "vocab.txt".
  </pre>
  
  <code>optional string filename = 2;</code>