'Evaluates the redshift dependence of the dark energy density.
Parameters
z : array-like
Input redshifts.
Returns
I : ndarray, or float if input scalar
The scaling of the energy density of dark energy with redshift.
Notes
The scaling factor, I, is defined by :math:`\rho(z) = \rho_0 I`,
and in this case is given by :math:`I = 1`.'

def de_density_scale(self, z):

    if np.isscalar(z):
        return 1.0
    else:
        return np.ones(np.asanyarray(z).shape, dtype=np.float)
