Add reorder-python-import pre-commit hook

Also updated README.md

Change-Id: I118309c61f4d00e8508d6b888c606995490fba39
Signed-off-by: Diego Russo <diego.russo@arm.com>
diff --git a/ethosu/vela/extract_npu_subgraphs.py b/ethosu/vela/extract_npu_subgraphs.py
index ab3db21..6747ec9 100644
--- a/ethosu/vela/extract_npu_subgraphs.py
+++ b/ethosu/vela/extract_npu_subgraphs.py
@@ -13,8 +13,6 @@
 # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
-
 # Description:
 # Vela separates CPU operations and NPU operations into separate internal subgraphs. The CPU operations are left
 # untouched in the final output.
@@ -22,11 +20,13 @@
 # Vela does this by identifying NPU passes and pulling them out from the main CPU graph into separate subgraphs, invoked
 # by NpuOp operations. Later, Vela generates command streams and compressed weight streams for the NPU subgraphs and
 # attaches them to the NpuOp. This encapsulates everything the NPU subgraph is supposed to do.
-
 import numpy as np
 
-from .nn_graph import Pass, PassPlacement, Subgraph
-from .operation import Operation, NpuBlockType
+from .nn_graph import Pass
+from .nn_graph import PassPlacement
+from .nn_graph import Subgraph
+from .operation import NpuBlockType
+from .operation import Operation
 
 
 def make_npu_call_op_pass(npu_subgraph):