>>> graph.pauli_matrix("I", name="identity")
<Tensor: name="identity", operation_name="pauli_matrix", shape=(2, 2)>
>>> result = qctrl.functions.calculate_graph(graph=graph, output_node_names=["identity"])
>>> result.output["identity"]["value"]
array([[1.+0.j, 0.+0.j],
[0.+0.j, 1.+0.j]])