title: Dynamically change dropdown options when one option is selected in Python Dash
body: <p>I have a dropdown of 4 values, ['All', 'a', 'b', 'c'], where I can select many of them.</p>
  <pre><code>dcc.Dropdown(
      id='test',
      options=[{'label': i, 'value': i} for i in ['All', 'a', 'b', 'c']],
      value='All',
      clearable=False,
      multi=True,
  ),
  </code></pre>
  <p>Now, is it possible to dynamically change the options, such that when 'All' is used, all other selected entries are removed automatically?
  Something like this:</p>
  <pre><code>@app.callback(
      Output('test', 'options'),
      Input('test', 'value'),
  )
  def update_ticker_options(value):
      if 'All' in value:
          ticker = 'All'
      return ticker
  </code></pre>
  <p>The app is not starting with this code, so it is not working.</p>