title: My question is about material-ui 4, material-ui/pickers compaining of inexistent "mask" property
body: <p>Upgraded a reactjs project using Material-UI (mui) from v3 to v4 and following the recommended migration guide.
  As part of that replaced material-ui-pickers 2.2.1 to  @material-ui/pickers.</p>
  
  <p>DatePicker components now complain of inexistent "mask" property which used to work fine on mui3.</p>
  
  <p>Migration guide nothing mentions about Pickers. So I wonder.
  For now I rolled back to using mui 3.9 and material-ui-pickers 2.2.1.</p>
  
  <pre><code>import { DatePicker, DateTimePicker } from '@material-ui/pickers';
  
  // later on...
  
  return (
      &lt;DatePicker
        name={name}
        value={value}
        clearable
        autoOk
        onChange={handleChange}
        format="DD/MM/YYYY"
        placeholder="___/___/______"
        mask={masked(value)}         // &lt;=== The mask property
        {...other}
      /&gt;
    );
  </code></pre>
  
  <p>Expected behaviour is DatePicker should work as in mui v3 since nothing is mentioned on the migration guide.</p>
  
  <p>Actual is the mask property no longer exists for the component.</p>