'Return the density parameter for dark matter at redshift ``z``.
Parameters
z : array-like
Input redshifts.
Returns
Odm : ndarray, or float if input scalar
The density of non-relativistic dark matter relative to the critical
density at each redshift.
Raises
ValueError
If Ob0 is None.
Notes
This does not include neutrinos, even if non-relativistic
at the redshift of interest.'

def Odm(self, z):

    if (self._Odm0 is None):
        raise ValueError(u'Baryonic    density    not    set    for    this    cosmology,    unclear    meaning    of    dark    matter    density')
    if isiterable(z):
        z = np.asarray(z)
    return ((self._Odm0 * ((1.0 + z) ** 3)) * (self.inv_efunc(z) ** 2))
