title: jsonlite array of arrays
body: <p>when using <code>jsonlite</code> to import a json that has an array inside other array I get an undesired unnamed list. Exemple below:</p>
  <pre><code>myjson=jsonlite::fromJSON('{
    &quot;class&quot; : &quot;human&quot;,
    &quot;type&quot; : [{ 
    &quot;shape&quot;:&quot;thin&quot;,
    &quot;face&quot;:[{&quot;eyes&quot;:&quot;blues&quot;,&quot;hair&quot;:&quot;brown&quot;}]
  }]
  }')
  
  str(myjson)
  
  List of 2
   $ class: chr &quot;human&quot;
   $ type :'data.frame':  1 obs. of  2 variables:
    ..$ shape: chr &quot;thin&quot;
    ..$ face :List of 1
    .. ..$ :'data.frame': 1 obs. of  2 variables:
    .. .. ..$ eyes: chr &quot;blues&quot;
    .. .. ..$ hair: chr &quot;brown&quot;
  </code></pre>
  <p>I would like to access the &quot;eyes&quot; field as below (however it doesn't work):</p>
  <pre><code>myjson[[&quot;type&quot;]][[&quot;face&quot;]][[&quot;eyes&quot;]]
  NULL
  </code></pre>
  <p>Instead, I need to add &quot;[[1]]&quot; in order to make it works:</p>
  <pre><code>myjson[[&quot;type&quot;]][[&quot;face&quot;]][[1]][[&quot;eyes&quot;]]
  [1] &quot;blues&quot;
  </code></pre>
  <p>Any ideas how could I format the json to get rid of this unnamed list?</p>