Lifted shape function to class scope

src/qibotn/QiboCircuitConvertor.py

@@ -17,12 +17,6 @@ class QiboCircuitToEinsum:
     """
 
     def __init__(self, circuit, dtype="complex128"):
-        def op_shape_from_qubits(nqubits):
-            """This function is to modify the shape of the tensor to the required format by cuQuantum
-            (qubit_states,) * input_output * qubits_involved
-            """
-            return (2, 2) * nqubits
-
         self.backend = cp
         self.dtype = getattr(self.backend, dtype)
 
@@ -35,7 +29,7 @@ class QiboCircuitToEinsum:
 
             # self.gate_tensors is to extract into a list the gate matrix together with the qubit id that it is acting on
             # https://github.com/NVIDIA/cuQuantum/blob/6b6339358f859ea930907b79854b90b2db71ab92/python/cuquantum/cutensornet/_internal/circuit_parser_utils_cirq.py#L32
-            required_shape = op_shape_from_qubits(len(gate_qubits))
+            required_shape = self.op_shape_from_qubits(len(gate_qubits))
             self.gate_tensors.append(
                 (
                     cp.asarray(gate.matrix).reshape(required_shape),
@@ -108,3 +102,9 @@ class QiboCircuitToEinsum:
                 next_frontier += 1
             mode_labels.append(output_mode_labels + input_mode_labels)
         return mode_labels, operands
+
+    def op_shape_from_qubits(self, nqubits):
+        """This function is to modify the shape of the tensor to the required format by cuQuantum
+        (qubit_states,) * input_output * qubits_involved
+        """
+        return (2, 2) * nqubits