public com.google.protobuf.ByteString getMidBytes() {
        java.lang.Object ref = mid_;
        if (ref instanceof String) {
          com.google.protobuf.ByteString b =
              com.google.protobuf.ByteString.copyFromUtf8((java.lang.String) ref);
          mid_ = b;
          return b;
        } else {
          return (com.google.protobuf.ByteString) ref;
        }
      }
<pre>
Object ID that should align with EntityAnnotation mid.
</pre>

<code>string mid = 1;</code>

@return The bytes for mid.
java-vision/proto-google-cloud-vision-v1/src/main/java/com/google/cloud/vision/v1/ProductSearchResults.java