def extrusion(target, throat_length='throat.length', throat_area='throat.area'
    ):
    """
    Calculate throat volume from the throat area and the throat length. This
    method is useful for abnormal shaped throats.

    Parameters
    ----------
    target : OpenPNM Object
        The object which this model is associated with. This controls the
        length of the calculated array, and also provides access to other
        necessary properties.

    throat_length and throat_area : strings
        The dictionary keys containing the arrays with the throat area and
        length values.

    Returns
    -------
    value : NumPy ndarray
        Array containing throat volume values.

    Notes
    -----
    At present this models does NOT account for the volume reprsented by the
    intersection of the throat with a spherical pore body.

    """
    leng = target[throat_length]
    area = target[throat_area]
    value = leng * area
    return value
