def invert(target, prop):
    """
    Inverts the given array

    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.

    prop : string
        Dictionary key pointing the values to invert

    """
    return 1.0 / target[prop]
