diff --git a/src/qibotn/backends/__init__.py b/src/qibotn/backends/__init__.py
index 4e0d026..624ed62 100644
--- a/src/qibotn/backends/__init__.py
+++ b/src/qibotn/backends/__init__.py
@@ -2,10 +2,10 @@ from typing import Union
 
 from qibo.config import raise_error
 
-from qibotn.backends.cutensornet import CuTensorNet  # pylint: disable=E0401
-from qibotn.backends.quimb import QuimbBackend  # pylint: disable=E0401
-from qibotn.backends.qmatchatea import QMatchaTeaBackend # pylint: disable=E0401
 from qibotn.backends.abstract import QibotnBackend
+from qibotn.backends.cutensornet import CuTensorNet  # pylint: disable=E0401
+from qibotn.backends.qmatchatea import QMatchaTeaBackend  # pylint: disable=E0401
+from qibotn.backends.quimb import QuimbBackend  # pylint: disable=E0401
 
 QibotnBackend = Union[CuTensorNet, QuimbBackend, QMatchaTeaBackend]
 
diff --git a/src/qibotn/backends/abstract.py b/src/qibotn/backends/abstract.py
index 6e8088d..f7d2df2 100644
--- a/src/qibotn/backends/abstract.py
+++ b/src/qibotn/backends/abstract.py
@@ -1,11 +1,11 @@
 from abc import abstractmethod
+
 from qibo.backends.numpy import NumpyBackend
 from qibo.config import raise_error
 
-
 DEFAULT_CONFIGURATION = {
-    "MPI_enabled": False,   # TODO: cutensornet specific, TBRemoved 
-    "NCCL_enabled": False,  # TODO: cutensornet specific, TBRemoved 
+    "MPI_enabled": False,  # TODO: cutensornet specific, TBRemoved
+    "NCCL_enabled": False,  # TODO: cutensornet specific, TBRemoved
     "expectation_enabled": False,
     "pauli_string_pattern": None,
     "MPS_enabled": False,
@@ -14,10 +14,9 @@ DEFAULT_CONFIGURATION = {
 }
 
 
-
 class QibotnBackend(NumpyBackend):
 
-    def __init__(self, runcard:dict = DEFAULT_CONFIGURATION):
+    def __init__(self, runcard: dict = DEFAULT_CONFIGURATION):
         super().__init__()
 
     def apply_gate(self, gate, state, nqubits):  # pragma: no cover
@@ -32,10 +31,8 @@ class QibotnBackend(NumpyBackend):
     def set_precision(self, precision):
         if precision != self.precision:
             super().set_precision(precision)
-    
+
     @abstractmethod
     def configure_tn_simulation(self, **config):
         """Configure the TN simulation that will be performed."""
         pass
-
-    
diff --git a/src/qibotn/backends/cutensornet.py b/src/qibotn/backends/cutensornet.py
index d4f1bcc..d02fdd5 100644
--- a/src/qibotn/backends/cutensornet.py
+++ b/src/qibotn/backends/cutensornet.py
@@ -82,7 +82,6 @@ class CuTensorNet(QibotnBackend):  # pragma: no cover
         if hasattr(self, "cutn"):
             self.cutn.destroy(self.handle)
 
-
     def cuda_type(self, dtype="complex64"):
         """Get CUDA Type.
 
diff --git a/src/qibotn/backends/quimb.py b/src/qibotn/backends/quimb.py
index 20223b3..30ef888 100644
--- a/src/qibotn/backends/quimb.py
+++ b/src/qibotn/backends/quimb.py
@@ -1,4 +1,3 @@
-from qibo.backends.numpy import NumpyBackend
 from qibo.config import raise_error
 from qibo.result import QuantumState
 
@@ -38,7 +37,6 @@ class QuimbBackend(QibotnBackend):
         self.platform = "QuimbBackend"
         self.versions["quimb"] = self.quimb.__version__
 
-
     def execute_circuit(
         self, circuit, initial_state=None, nshots=None, return_array=False
     ):  # pragma: no cover