title: How to do a nested sum with multiplication in gurobi python for a MILP problem
body: <p>I am new to python and I have started doing optimization using gurobi in python.</p>
  <p>I am stuck at writing the first constraint.</p>
  <p>I have searched multiple documentation but unable to find it.</p>
  <p>It is nested sum for multiple items using multiplication.</p>
  <p>Can anyone help me in the same?</p>
  <p>Thanks in advance.</p>
  <pre><code>[This is the constraint I am trying to formulate][1]
  
  
    [1]: https://i.stack.imgur.com/XkzLa.jpg
  </code></pre>