an class="emphasis"><em>asymmetric_coroutine&lt;&gt;::pull_type</em></span>
        is passed as argument to <span class="emphasis"><em>coroutine-function</em></span>. The main-context
        must call this <span class="emphasis"><em>asymmetric_coroutine&lt;&gt;::push_type::operator()</em></span>
        in order to transfer each data value into the <span class="emphasis"><em>coroutine-function</em></span>.
        Access to the transferred data value is given by <span class="emphasis"><em>asymmetric_corou