@java.lang.Override
  public /* nullable */ java.lang.String getHeadersOrDefault(
      java.lang.String key,
      /* nullable */
      java.lang.String defaultValue) {
    if (key == null) {
      throw new NullPointerException("map key");
    }
    java.util.Map<java.lang.String, java.lang.String> map = internalGetHeaders().getMap();
    return map.containsKey(key) ? map.get(key) : defaultValue;
  }
<pre>
Custom headers to pass into fetch request.
Headers must have a maximum of 3 key value pairs.
Each key value pair must have a maximum of 256 characters per key and 256
characters per value.
</pre>

<code>map&lt;string, string&gt; headers = 1;</code>
java-video-stitcher/proto-google-cloud-video-stitcher-v1/src/main/java/com/google/cloud/video/stitcher/v1/FetchOptions.java