def spectral_density_args_kwargs(kwargs):
    """
    This helper function separates positional arguments and keyword arguments
    for the spectral_density function from a dictionary of both that is
    easy to use in parameterized tests.
    """

    # Pull out the non-keyword arguments
    args = (
        kwargs["wavelengths"],
        kwargs["probe_wavelength"],
        kwargs["n"],
    )

    del kwargs["wavelengths"]
    del kwargs["probe_wavelength"]
    del kwargs["n"]

    return args, kwargs