listeners.add(new PerListenerQueue<>(listener, executor));
  }

  /**
   * Enqueues an event to be run on currently known listeners.
   *
   * <p>The {@code toString} method of the Event itself will be used to describe the event in the
   * case of an error.
   *
   * @param event the callback to execute on {@link #dispatch}
   */
  public void enqueue(Event<L> event) {
    enqueueHelper(event, event);
  }

  /**

  // +listType=atomic
  // +optional
  repeated IngressRule rules = 3;
}

// IngressStatus describe the current state of the Ingress.
message IngressStatus {
  // loadBalancer contains the current status of the load-balancer.
  // +optional
  optional IngressLoadBalancerStatus loadBalancer = 1;
}

// IngressTLS describes the transport layer security associated with an ingress.
message IngressTLS {

   with respect to some or all of the Covered Software due to statute, judicial
   order, or regulation then You must: (a) comply with the terms of this License
   to the maximum extent possible; and (b) describe the limitations and the code
   they affect. Such description must be placed in a text file included with all
   distributions of the Covered Software under this License. Except to the

   with respect to some or all of the Covered Software due to statute,
   judicial order, or regulation then You must: (a) comply with the terms of
   this License to the maximum extent possible; and (b) describe the
   limitations and the code they affect. Such description must be placed in a
   text file included with all distributions of the Covered Software under

That means that, clients using your API don't have to check if the value exists or not, they can **assume the field will always be there**, but just that in some cases it will have the default value of `None`.

The way to describe this in OpenAPI, is to mark that field as **required**, because it will always be there.

Because of that, the JSON Schema for a model can be different depending on if it's used for **input or output**:

  // This field is beta-level in 1.8
  // +optional
  repeated string policyTypes = 4;
}

// NetworkPolicyStatus describe the current state of the NetworkPolicy.
message NetworkPolicyStatus {
  // Conditions holds an array of metav1.Condition that describe the state of the NetworkPolicy.
  // Current service state
  // +optional
  // +patchMergeKey=type
  // +patchStrategy=merge
  // +listType=map

   with respect to some or all of the Covered Software due to statute, judicial
   order, or regulation then You must: (a) comply with the terms of this License
   to the maximum extent possible; and (b) describe the limitations and the code
   they affect. Such description must be placed in a text file included with all
   distributions of the Covered Software under this License. Except to the

   with respect to some or all of the Covered Software due to statute, judicial
   order, or regulation then You must: (a) comply with the terms of this License
   to the maximum extent possible; and (b) describe the limitations and the code
   they affect. Such description must be placed in a text file included with all
   distributions of the Covered Software under this License. Except to the

          <name>licenses</name>
          <version>3.0.0+</version>
          <description>
            <![CDATA[
            This element describes all the licenses for this project.
            Each license is described by a {@code license} element, which
            is then described by additional elements.
            Projects should only list the license(s) that applies to the project

		desc:          prometheus.NewDesc("minio_bucket_stats", "Statistics exposed by MinIO server cluster wide per bucket", nil, nil),
	}
}

// Describe sends the super-set of all possible descriptors of metrics
func (c *minioBucketCollector) Describe(ch chan<- *prometheus.Desc) {
	ch <- c.desc
}

// Collect is called by the Prometheus registry when collecting metrics.