ass="sd">    This is useful, for instance, when you want to mix training, validation, sampling steps within an epoch.</span>

<span class="sd">    You can give it tuples of iterator names and iterators.</span>
<span class="sd">    It will yield the names along with the iterator values.</span>

<span class="sd">    If you pass a function instead of a name it will call that function with the iterator value, instead of</span>
<span class="sd">    yielding it.</span>

<span class="sd">    Arguments:</span>
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