me">registerUnaryCallback</span>: <span class="default-value">null</span>, </span> <span class="parameter" id="from-param-registerBinaryCallback"><span class="type-annotation"><a href="dart-async/RegisterBinaryCallbackHandler.html">RegisterBinaryCallbackHandler</a><span class="signature">&lt;R, T1, T2&gt;</span></span> <span class="parameter-name">registerBinaryCallback</span>: <span class="default-value">null</span>, </span> <span class="parameter" id="from-param-errorCallback"><span class="type-annotation