title: How to access other Store records from Model's convert method in ExtJS6?
body: <p>I am trying to have a calculated field inside a Model that looks something like <code>value (maxValue)</code>, where <code>maxValue</code> is the maximum value among all other records currently loaded (think current page of a Grid).</p>
  
  <p>Model:</p>
  
  <pre><code>Ext.define('MyApp.model.Example', {
      extend: 'Ext.data.Model',
      fields: [
          {name: 'id'},
          {name: 'value'},
          {name: 'calculated_value', convert: function(value, record){
              //how to access all the records here, not just the current one?
          }}
      ]
  });
  </code></pre>