code: public com.google.protobuf.Struct getSystemLabels() {
      return systemLabels_ == null ? com.google.protobuf.Struct.getDefaultInstance() : systemLabels_;
    }
docs: <pre>
  Output only. Values for predefined system metadata labels.
  System labels are a kind of metadata extracted by Google, including
  "machine_image", "vpc", "subnet_id",
  "security_group", "name", etc.
  System label values can be only strings, Boolean values, or a list of
  strings. For example:
  { "name": "my-test-instance",
  "security_group": ["a", "b", "c"],
  "spot_instance": false }
  </pre>
  
  <code>.google.protobuf.Struct system_labels = 1;</code>