private void ensureFramesIsMutable() {
      if (!((bitField0_ & 0x00000004) != 0)) {
        frames_ =
            new java.util.ArrayList<com.google.cloud.videointelligence.v1p3beta1.TextFrame>(
                frames_);
        bitField0_ |= 0x00000004;
      }
    }
<pre>
Confidence for the track of detected text. It is calculated as the highest
over all frames where OCR detected text appears.
</pre>

<code>float confidence = 2;</code>

@return This builder for chaining.
java-video-intelligence/proto-google-cloud-video-intelligence-v1p3beta1/src/main/java/com/google/cloud/videointelligence/v1p3beta1/TextSegment.java