def METHOD_NAME(op, format="prefactor"):
    r"""Returns the generator of an operation.
    Args:
        op (.Operator or Callable): A single operator, or a function that
            applies a single quantum operation.
        format (str): The format to return the generator in. Must be one of ``'prefactor'``,
            ``'observable'``, or ``'hamiltonian'``. See below for more details.
    Returns:
        .Operator or tuple[.Observable, float]: The returned generator, with format/type
        dependent on the ``format`` argument.
        * ``"prefactor"``: Return the generator as ``(obs, prefactor)`` (representing
          :math:`G=p \hat{O}`), where:
          - observable :math:`\hat{O}` is one of :class:`~.Hermitian`,
            :class:`~.SparseHamiltonian`, or a tensor product
            of Pauli words.
          - prefactor :math:`p` is a float.
        * ``"observable"``: Return the generator as a single observable as directly defined
          by ``op``. Returned generators may be any type of observable, including
          :class:`~.Hermitian`, :class:`~.Tensor`,
          :class:`~.SparseHamiltonian`, or :class:`~.Hamiltonian`.
        * ``"hamiltonian"``: Similar to ``"observable"``, however the returned observable
          will always be converted into :class:`~.Hamiltonian` regardless of how ``op``
          encodes the generator.
        * ``"arithmetic"``: Similar to ``"hamiltonian"``, however the returned observable
          will always be converted into an arithmetic operator. The returned generator may be
          any type, including:
          :class:`~.ops.op_math.SProd`, :class:`~.ops.op_math.Prod`, :class:`~.ops.op_math.Sum`, or the operator itself.
    **Example**
    Given an operation, ``qml.generator`` returns the generator representation:
    >>> op = qml.CRX(0.6, wires=[0, 1])
    >>> qml.generator(op)
    (Projector([1], wires=[0]) @ PauliX(wires=[1]), -0.5)
    It can also be used in a functional form:
    >>> qml.generator(qml.CRX)(0.6, wires=[0, 1])
    (Projector([1], wires=[0]) @ PauliX(wires=[1]), -0.5)
    By default, ``generator`` will return the generator in the format of ``(obs, prefactor)``,
    corresponding to :math:`G=p \hat{O}`, where the observable :math:`\hat{O}` will
    always be given in tensor product form, or as a dense/sparse matrix.
    By using the ``format`` argument, the returned generator representation can
    be altered:
    >>> op = qml.RX(0.2, wires=0)
    >>> qml.generator(op, format="prefactor")  # output will always be (obs, prefactor)
    (PauliX(wires=[0]), -0.5)
    >>> qml.generator(op, format="hamiltonian")  # output will always be a Hamiltonian
    <Hamiltonian: terms=1, wires=[0]>
    >>> qml.generator(qml.PhaseShift(0.1, wires=0), format="observable")  # ouput will be a simplified obs where possible
    Projector([1], wires=[0])
    >>> qml.generator(op, format="arithmetic")  # output is an instance of `SProd`
    -0.5*(PauliX(wires=[0]))
    """
    if op.num_params != 1:
        raise ValueError(f"Operation {op.name} is not written in terms of a single parameter")
    try:
        gen = op.METHOD_NAME()
    except TypeError:
        # For backwards compatibility with PennyLane
        # versions <=0.22, assume op.generator is a property
        gen = _generator_backcompatibility(op)
    if not gen.is_hermitian:
        raise qml.QuantumFunctionError(
            f"Generator {gen.name} of operation {op.name} is not hermitian"
        )
    if format == "prefactor":
        return _generator_prefactor(gen)
    if format == "hamiltonian":
        return _generator_hamiltonian(gen, op)
    if format == "arithmetic":
        h = _generator_hamiltonian(gen, op)
        return qml.dot(h.coeffs, h.ops)
    if format == "observable":
        return gen
    raise ValueError(
        "format must be one of ('prefactor', 'hamiltonian', 'observable', 'arithmetic')"
    )