+ rho**2*TensorProduct(dtheta, dtheta)
    >>> riemann = metric_to_Riemann_components(non_trivial_metric)
    >>> riemann[0, :, :, :]
    [[[0, 0], [0, 0]], [[0, exp(-2*rho)*rho], [-exp(-2*rho)*rho, 0]]]
    >>> riemann[1, :, :, :]
    [[[0, -1/rho], [1/rho, 0]], [[0, 0], [0, 0]]]

    c