title: Intersect two dictionaries
body: <p>Let's say I have two dictionaries as following:</p>
  
  <pre><code>dict1 = {vessel1: [a, b, c], vessel2: [a, d, e], ...}
  
  dict2 = {operation1: [a, d], operation2: [a, e, b], ...}
  </code></pre>
  
  <p>Each dictionary (<code>dict1</code>, <code>dict2</code>) is a dictionary of dictionaries, so that <code>a</code>, <code>b</code>, <code>c</code>, <code>d</code>, <code>e</code>, <code>f</code> and <code>g</code> are dictionaries too.</p>
  
  <p>What I want is, for example, intersect <code>dict1(vessel1)</code> with <code>dict2(operation2)</code>, and have a result dictionary as following:</p>
  
  <pre><code>result_dictionary_of_intersection = [a, b]
  </code></pre>
  
  <p>I.e., have a result dictionary that only contains items that both vessel1 and operation2 have. </p>
  
  <p>Remembering: <code>a</code> and <code>b</code> are dictionaries too.</p>