title: RF 3.0.4 nested dictionary syntax error if first key is number, dot notation doesn't work
body: <p>I am using <code>rf 3.0.4.</code> I upgraded because of the dot notation upgrade (before I was using <code>rf 2.9</code>).
  My problem is when I want to access a nested dictionary item and the first key (it is an id from db) is a number, I got a syntax error.</p>
  
  <p>I have a nested dictionary: <code>&amp;{Attributes}</code> </p>
  
  <p>So what I want to do:</p>
  
  <pre><code>${Attributes.1000.name}
  </code></pre>
  
  <p>The syntax error I get:</p>
  
  <p>Resolving variable <code>'${Attributes.1000.name}' failed: SyntaxError: invalid syntax (&lt;string&gt;, line 1)</code></p>
  
  <p>And what is working:</p>
  
  <pre><code>${Attributes["1000"]["name"]}
  </code></pre>
  
  <p>I'd like to use the dot notation, because it is more readable.
  Do any of you know why it doesn't work?</p>