def METHOD_NAME(op: Operator):
    r"""Expectation value of the supplied observable.
    **Example:**
    .. code-block:: python3
        dev = qml.device("default.qubit", wires=2)
        @qml.qnode(dev)
        def circuit(x):
            qml.RX(x, wires=0)
            qml.Hadamard(wires=1)
            qml.CNOT(wires=[0, 1])
            return qml.expval(qml.PauliY(0))
    Executing this QNode:
    >>> circuit(0.5)
    -0.4794255386042029
    Args:
        op (Observable): a quantum observable object
    Returns:
        ExpectationMP: measurement process instance
    """
    if not op.is_hermitian:
        warnings.warn(f"{op.name} might not be hermitian.")
    return ExpectationMP(obs=op)