code: def set_energy(self, spins, target_energy):
          
          spin_energy = self.energy(spins)
          self.assertions.add(Equals(spin_energy, limitReal(target_energy)))
docs: Set the energy of Theta with spins fixed to target_energy.
  
          Args:
              spins (dict): Spin values for a subset of the variables in Theta.
              target_energy (float): The desired energy for Theta with spins fixed.
  
          Notes:
              Add equality constraint to assertions.