'Return the equivalent density parameter for curvature
at redshift ``z``.
Parameters
z : array-like
Input redshifts.
Returns
Ok : ndarray, or float if input scalar
The equivalent density parameter for curvature at each redshift.'

def Ok(self, z):

    if isiterable(z):
        z = np.asarray(z)
        if (self._Ok0 == 0):
            return np.zeros(np.asanyarray(z).shape, dtype=np.float)
    elif (self._Ok0 == 0):
        return 0.0
    return ((self._Ok0 * ((1.0 + z) ** 2)) * (self.inv_efunc(z) ** 2))
