-flagOptional">Optional</span> options: <span class="tsd-signature-type">any</span></h5></li><li><h5><span class="tsd-flag ts-flagOptional">Optional</span> progressCallback: <span class="tsd-signature-type">ProgressCallback</span></h5></li></ul><h4 class="tsd-returns-title">Returns <span class="tsd-signature-type">Promise</span><span class="tsd-signature-symbol">&lt;</span><span class="tsd-signature-type">string</span><span class="tsd-signature-symbol">&gt;</span></h4></li></ul></section><section class="tsd