<h4 dir="auto">Describe the bug</h4>

<h4 dir="auto">Steps/Code to Reproduce</h4>

<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="To duplicate the issue, please refer to attached zip file. In there you will find a copy of Python script and input data set"><pre class="notranslate"><code class="notranslate">To duplicate the issue, please refer to attached zip file. In there you will find a copy of Python script and input data set
</code></pre></div>
<h4 dir="auto">Expected Results</h4>

<h4 dir="auto">Actual Results</h4>

<h4 dir="auto">Versions</h4>

<p dir="auto">scikit-learn --&gt; 0.24.2<br>
numpy --&gt; 1.19.5<br>
scipy --&gt; 1.5.4<br>
imblearn --&gt; 0.8.0<br>
platform --&gt; Windows-10-10.0.19041-SP0<br>
sys --&gt; 3.6.5 (v3.6.5:f59c0932b4, Mar 28 2018, 17:00:18) [MSC v.1900 64 bit (AMD64)]</p>

<p dir="auto"><a href="https://github.com/scikit-learn/scikit-learn/files/6576764/test_chunked_pairwise_distances.zip">test_chunked_pairwise_distances.zip</a></p>
<p dir="auto">Saw this piece of code when reading the implementation of <code class="notranslate">VotingClassifier</code></p>
<div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="if isinstance(y, np.ndarray) and len(y.shape) &gt; 1 and y.shape[1] &gt; 1:                                           
        raise NotImplementedError('Multilabel and multi-output'                                                     
                                                     ' classification is not supported.')                                              "><pre class="notranslate"><span class="pl-k">if</span> <span class="pl-en">isinstance</span>(<span class="pl-s1">y</span>, <span class="pl-s1">np</span>.<span class="pl-s1">ndarray</span>) <span class="pl-c1">and</span> <span class="pl-en">len</span>(<span class="pl-s1">y</span>.<span class="pl-s1">shape</span>) <span class="pl-c1">&gt;</span> <span class="pl-c1">1</span> <span class="pl-c1">and</span> <span class="pl-s1">y</span>.<span class="pl-s1">shape</span>[<span class="pl-c1">1</span>] <span class="pl-c1">&gt;</span> <span class="pl-c1">1</span>:                                           
        <span class="pl-k">raise</span> <span class="pl-v">NotImplementedError</span>(<span class="pl-s">'Multilabel and multi-output'</span>                                                     
                                                     <span class="pl-s">' classification is not supported.'</span>)                                              </pre></div>
<p dir="auto">Is this due to some blocker or challenge? Thanks</p>