@SuppressWarnings({"rawtypes"})
    protected com.google.protobuf.MapFieldReflectionAccessor internalGetMutableMapFieldReflection(
        int number) {
      switch (number) {
        case 4:
          return internalGetMutableLabels();
        default:
          throw new RuntimeException("Invalid map field number: " + number);
      }
    }
<pre>
Source message describes a specific vm migration Source resource. It contains
the source environment information.
</pre>

Protobuf type {@code google.cloud.vmmigration.v1.Source}
java-vmmigration/proto-google-cloud-vmmigration-v1/src/main/java/com/google/cloud/vmmigration/v1/Source.java