code: def _get_facvar(self, polynomial):
          
          facvar = [0] * (self.n_vars + 1)
          # Preprocess the polynomial for uniform handling later
          if is_number_type(polynomial):
              facvar[0] = polynomial
              return facvar
          polynomial = polynomial.expand()
          if polynomial.is_Mul:
              elements = [polynomial]
          else:
              elements = polynomial.as_coeff_mul()[1][0].as_coeff_add()[1]
          for element in elements:
              results = self._get_index_of_monomial(element)
              for (k, coeff) in results:
                  facvar[k] += coeff
          return facvar
docs: Return dense vector representation of a polynomial. This function is
          nearly identical to __push_facvar_sparse, but instead of pushing
          sparse entries to the constraint matrices, it returns a dense
          vector.