Remove unused imports, format it using black

tests/test_cuquantum_cutensor_backend.py

@@ -1,5 +1,3 @@
-import copy
-import os
 from timeit import default_timer as timer
 
 import config
@@ -22,18 +20,22 @@ def time(func):
     time = end - start
     return time, res
 
+
 @pytest.mark.gpu
 @pytest.mark.parametrize("nqubits", [1, 2, 5, 10])
 def test_eval(nqubits: int):
     import qibotn.cutn
 
     # Test qibo
-    qibo.set_backend(backend=config.qibo.backend, platform=config.qibo.platform)
-    qibo_time, (qibo_circ, result_sv) = time(lambda: qibo_qft(nqubits, swaps=True))
+    qibo.set_backend(backend=config.qibo.backend,
+                     platform=config.qibo.platform)
+    qibo_time, (qibo_circ, result_sv) = time(
+        lambda: qibo_qft(nqubits, swaps=True))
 
     # Test Cuquantum
     data_type = "complex128"
     cutn_time, result_tn = time(lambda: qibotn.cutn.eval(qibo_circ, data_type))
 
     assert 1e-2 * qibo_time < cutn_time < 1e2 * qibo_time
-    assert np.allclose(result_sv, result_tn), "Resulting dense vectors do not match"
+    assert np.allclose(
+        result_sv, result_tn), "Resulting dense vectors do not match"