title: DataStudio - Failed to retrieve data from the underlying data set
body: <p>I made a custom connector (plugged to an API) in DataStudio, but when I tried to create a report I get this error <code>Failed to retrieve data from the underlying data set.</code>.   </p>
  
  <p>My connector give to field in the asked order, not all the fields, only the ones requested, but I still have this error.   </p>
  
  <p>Is anyone can help me?</p>
  
  <p><strong>FIX</strong>  </p>
  
  <p>My return data struture wasn't good...
  Here is the good format : </p>
  
  <pre><code>{ schema: 
    [ { dataType: 'STRING',
        name: 'firstname',
        semantics: [Object],
        label: 'Firstname' },
     { dataType: 'NUMBER',
     name: 'id',
     semantics: [Object],
     label: 'Id' } ],
  rows: 
   [ ['Bob',48526], ['Robert', 4994], ...] }
  </code></pre>