private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.vmmigration.v1.Source,
            com.google.cloud.vmmigration.v1.Source.Builder,
            com.google.cloud.vmmigration.v1.SourceOrBuilder>
        getSourceFieldBuilder() {
      if (sourceBuilder_ == null) {
        sourceBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.vmmigration.v1.Source,
                com.google.cloud.vmmigration.v1.Source.Builder,
                com.google.cloud.vmmigration.v1.SourceOrBuilder>(
                getSource(), getParentForChildren(), isClean());
        source_ = null;
      }
      return sourceBuilder_;
    }
<pre>
Required. The update request body.
</pre>

<code>
.google.cloud.vmmigration.v1.Source source = 2 [(.google.api.field_behavior) = REQUIRED];
</code>
java-vmmigration/proto-google-cloud-vmmigration-v1/src/main/java/com/google/cloud/vmmigration/v1/UpdateSourceRequest.java