public Builder addProperties(com.google.cloud.vision.v1.Property value) {
      if (propertiesBuilder_ == null) {
        if (value == null) {
          throw new NullPointerException();
        }
        ensurePropertiesIsMutable();
        properties_.add(value);
        onChanged();
      } else {
        propertiesBuilder_.addMessage(value);
      }
      return this;
    }
<pre>
Some entities may have optional user-supplied `Property` (name/value)
fields, such a score or string that qualifies the entity.
</pre>

<code>repeated .google.cloud.vision.v1.Property properties = 9;</code>
java-vision/proto-google-cloud-vision-v1/src/main/java/com/google/cloud/vision/v1/EntityAnnotation.java