public static com.google.cloud.storagebatchoperations.v1.PutMetadata parseFrom(
      com.google.protobuf.ByteString data,
      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
      throws com.google.protobuf.InvalidProtocolBufferException {
    return PARSER.parseFrom(data, extensionRegistry);
  }
<pre>
Optional. Updates objects custom metadata. Adds or sets individual custom
metadata key value pairs on objects. Keys that are set with empty custom
metadata values will have its value cleared. Existing custom metadata not
specified with this flag is not changed. Refer to documentation in
https://cloud.google.com/storage/docs/metadata#custom-metadata
</pre>

<code>map&lt;string, string&gt; custom_metadata = 7 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-storagebatchoperations/proto-google-cloud-storagebatchoperations-v1/src/main/java/com/google/cloud/storagebatchoperations/v1/PutMetadata.java