title: Object is unknown type - Material UI
body: <p>This code is a direct copy from  the React Material UI site</p>
  <pre><code>    &lt;Select
                    id=&quot;selectedSubusecases&quot;
                    multiple
                    value={stepsState.campaignOverviewStep.selectedSubUsecases}
                    onChange={handleChangeMultiple}
                    input={&lt;Input id=&quot;select-multiple-chip&quot; /&gt;}
                    renderValue={selected =&gt; (
                      &lt;div className={classes.chips}&gt;
                        {selected.map(value =&gt; (
                          &lt;Chip
                            key={value}
                            label={value}
                            className={classes.chip}
                          /&gt;
                        ))}
                      &lt;/div&gt;
                    )}
                    MenuProps={SubusecaseMenuProps}
                  &gt;
  </code></pre>
  <p>But when I try to use it I get &quot;Object is of type unknown&quot; for &quot;selected&quot;
  <code>{selected.map(value =&gt; (</code></p>