>Gets a map containing extra parameters to pass to the listeners.

 <p>Returning map is optional and is useful for instrumentation purposes.

 <p>This map won't be modified by the caller.</p></div>
  <div class="jd-tagdata">
      <h5 class="jd-tagtitle">Parameters</h5>
      <table class="jd-tagtable">
        <tr>
          <th>fetchState</th>
          <td>the fetch-specific state</td>
        </tr>
        <tr>
          <th>byteSize</th>
          <td>size of the data in bytes</td>
        </tr>
      