title: Using CP-SAT Solver for non-linear objective function
body: <p>I'm trying to use CP-SAT solver with some variables: <code>x</code>,<code>y</code>. I want to maximise an objective function of the form <code>x**2-y*x</code> with some constraints. I'm getting</p>
  
  <blockquote>
    <p>TypeError: unsupported operand type(s) for ** or pow(): 'IntVar' and
    'int'</p>
  </blockquote>
  
  <p>error messages. Am I correct in assuming I cannot use nonlinear objective function for CP-SAT, as I couldn't find any documentation or examples that did employ nonlinear objectives? Or is there some way to do this?</p>