def assign_cosmo(cosmo, model=[70, 0.3, 0.7, -0.9, 0.0]):
    """Define a new cosmology model.

    Parameters
    ----------
    cosmo: astropy.cosmology Cosmology Object
        Assumes original cosmology was astropy.cosmology.w0waCDM.
    model: list (optional)
        Cosmology parameters: [H0, Om, Ode, w0, wa].
        Default is [70, 0.3, 0.7, -0.9, 0.0].
        Hard code Ob0 (Omega baryons) = 0.022

    Returns
    -------
    newcosmo: astropy.cosmology Cosmology Object
        New Cosmology Object with updated cosmology parameters
    """

    ob0=0.022
    om0=model[1]
    ode0 =model[2]

    newcosmo = cosmo.clone(name='temp cosmo', H0=model[0], Ob0=ob0,
                           Om0=om0, Ode0=ode0, w0=model[3], wa=model[4])

    return newcosmo