title: Using >= for constraint throws RuntimeError (please use pydrake.common.containers.EqualToDict)
body: <p>I am trying to use direct transcription to solve my trajectory optimization problem which involves some trigonometric functions.</p>
  
  <p>I have the following variable types</p>
  
  <pre><code>a[i] = array([&lt;Expression "(state_0(0) + 0.001 * state_0(4))"&gt;,
         &lt;Expression "(state_0(1) + 0.001 * state_0(5))"&gt;,
         &lt;Expression "(state_0(2) + 0.001 * state_0(6))"&gt;,
         &lt;Expression "(state_0(3) + 0.001 * state_0(7))"&gt;,
         &lt;Expression "...omitted..."&gt;,
         &lt;Expression "...omitted..."&gt;,
         &lt;Expression "...omitted..."&gt;,
         &lt;Expression "...omitted..."&gt;], dtype=object)
  
  b[i] = array([Variable('state_1(0)', Continuous),
         Variable('state_1(1)', Continuous),
         Variable('state_1(2)', Continuous),
         Variable('state_1(3)', Continuous),
         Variable('state_1(4)', Continuous),
         Variable('state_1(5)', Continuous),
         Variable('state_1(6)', Continuous),
         Variable('state_1(7)', Continuous)], dtype=object)
  </code></pre>
  
  <p>I'm trying to create a constraint as follows</p>
  
  <pre><code>mp.AddConstraint(b[i] &lt;= a[i])
  </code></pre>
  
  <p>But I get the following error</p>
  
  <pre><code>RuntimeError: You should not call `__bool__` / `__nonzero__` on `Formula`. If you are trying to make a map with `Variable`, `Expression`, or `Polynomial` as keys (and then access the map in Python), please use pydrake.common.containers.EqualToDict`.
  </code></pre>