Merge branch 'summary' of github.com:qiboteam/qibo into summary

Author: renatomello

doc/source/code-examples/examples.rst

@@ -83,7 +83,7 @@ For example
     circuit.add(gates.TOFFOLI(0, 1, 2))
 
     circuit.summary()
-    
+
     # Prints
     '''
     Circuit depth = 5

src/qibo/models/circuit.py

@@ -9,8 +9,9 @@
 import numpy as np
 from numpy.typing import ArrayLike
 from tabulate import tabulate
+
 from qibo import __version__, gates
-from qibo.backends import _check_backend, _Global, Backend
+from qibo.backends import Backend, _check_backend, _Global
 from qibo.config import raise_error
 from qibo.gates import ParametrizedGate
 from qibo.gates.abstract import Gate