message: adding to_numpy() to PauliOperator python api
diff: @@ -76,6 +76,15 @@ void bind_quantum(py::module &m) {
  .def("computeActionOnKet", &PauliOperator::computeActionOnKet)
  .def("computeActionOnBra", &PauliOperator::computeActionOnBra)
  .def("getNonIdentitySubTerms", &PauliOperator::getNonIdentitySubTerms)
  + .def("to_numpy", [](PauliOperator& op) {
  + auto mat_el = op.to_sparse_matrix();
  + auto size = std::pow(2, op.nBits());
  + Eigen::MatrixXcd mat = Eigen::MatrixXcd::Zero(size, size);
  + for (auto el : mat_el) {
  + mat(el.row(), el.col()) = el.coeff();
  + }
  + return mat;
  + })
  .def(
  "__iter__",
  [](PauliOperator &op) {
  