title: update a tuple key in dictionary with another dictionary in python
body: <p>I have:</p>
  <pre><code>edge_mask = {(0, 2): 0.7, (0, 6): 0.4}
  </code></pre>
  <p>and this:</p>
  <pre><code>labels: {0: 'A', 1: 'B', 2: 'C', 3: 'D', 4: 'E', 5: 'F', 6: 'G'}
  </code></pre>
  <p>I need to update the dictionary:</p>
  <pre><code>edge_mask = {('A', 'C'): 0.7, ('A', 'G'): 0.4}
  </code></pre>