code: public java.lang.String getFilename() {
      java.lang.Object ref = filename_;
      if (ref instanceof java.lang.String) {
        return (java.lang.String) ref;
      } else {
        com.google.protobuf.ByteString bs = 
            (com.google.protobuf.ByteString) ref;
        java.lang.String s = bs.toStringUtf8();
        filename_ = s;
        return s;
      }
    }
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>