Expose number preserving conversion function (#577)

* import sparse preserving function

* format

src/openfermion/transforms/__init__.py

@@ -10,36 +10,66 @@
 #   See the License for the specific language governing permissions and
 #   limitations under the License.
 
-from ._binary_code_transform import (binary_code_transform,
-                                     dissolve)
-from ._bksf import bravyi_kitaev_fast
-from ._binary_codes import (bravyi_kitaev_code,
-                            checksum_code,
-                            interleaved_code,
-                            jordan_wigner_code,
-                            linearize_decoder,
-                            parity_code,
-                            weight_one_binary_addressing_code,
-                            weight_one_segment_code,
-                            weight_two_segment_code)
-from ._bravyi_kitaev import bravyi_kitaev
-from ._bravyi_kitaev_tree import bravyi_kitaev_tree
-from ._conversion import (get_boson_operator,
-                          get_diagonal_coulomb_hamiltonian,
-                          get_fermion_operator,
-                          get_interaction_rdm,
-                          get_interaction_operator,
-                          get_quadratic_hamiltonian,
-                          get_molecular_data,
-                          get_sparse_operator,
-                          get_quad_operator)
-from ._jordan_wigner import jordan_wigner
-from ._qubit_operator_transforms import (project_onto_sector,
-                                         projection_error,
-                                         rotate_qubit_by_pauli)
-from ._reverse_jordan_wigner import reverse_jordan_wigner
-from ._verstraete_cirac import verstraete_cirac_2d_square
-from ._weyl_ordering import (symmetric_ordering,
-                             weyl_polynomial_quantization)
-from ._remove_symmetry_qubits import (symmetry_conserving_bravyi_kitaev,
-                                      edit_hamiltonian_for_spin)
+from ._binary_code_transform import (
+    binary_code_transform,
+    dissolve,
+)
+
+from ._bksf import (
+    bravyi_kitaev_fast,)
+
+from ._binary_codes import (
+    bravyi_kitaev_code,
+    checksum_code,
+    interleaved_code,
+    jordan_wigner_code,
+    linearize_decoder,
+    parity_code,
+    weight_one_binary_addressing_code,
+    weight_one_segment_code,
+    weight_two_segment_code,
+)
+
+from ._bravyi_kitaev import (
+    bravyi_kitaev,)
+
+from ._bravyi_kitaev_tree import (
+    bravyi_kitaev_tree,)
+
+from ._conversion import (
+    get_boson_operator,
+    get_diagonal_coulomb_hamiltonian,
+    get_fermion_operator,
+    get_interaction_rdm,
+    get_interaction_operator,
+    get_quadratic_hamiltonian,
+    get_molecular_data,
+    get_number_preserving_sparse_operator,
+    get_sparse_operator,
+    get_quad_operator,
+)
+
+from ._jordan_wigner import (
+    jordan_wigner,)
+
+from ._qubit_operator_transforms import (
+    project_onto_sector,
+    projection_error,
+    rotate_qubit_by_pauli,
+)
+
+from ._reverse_jordan_wigner import (
+    reverse_jordan_wigner,)
+
+from ._verstraete_cirac import (
+    verstraete_cirac_2d_square,)
+
+from ._weyl_ordering import (
+    symmetric_ordering,
+    weyl_polynomial_quantization,
+)
+
+from ._remove_symmetry_qubits import (
+    symmetry_conserving_bravyi_kitaev,
+    edit_hamiltonian_for_spin,
+)