title: Python Cerberus dependencies on nested list level
body: <p>Does <code>Cerberus 1.2</code> support dependency validation on a list? </p>
  
  <p>For instance the schema looks as follows:</p>
  
  <pre class="lang-py prettyprint-override"><code>schema = {
     'list_1': {
       'type': 'list',
       'schema': {
         'type': 'dict',
         'schema': {
           'simple_field': {'type': 'boolean'},
           'not_simple_field': {
             'type': 'dict',
             'schema': {
                'my_field': {'dependencies': {'simple_field': True}}
             }
           }
         }
       }
     }
   }
  </code></pre>
  
  <p>The rule that I'd like to check is that <code>my_field</code> should only exist when <code>simple_field</code> is True. How would I translate that in <code>Cerberus</code>?</p>