def METHOD_NAME():
    E_g = np.array([10.0, 7.5, 5.0, 2.5, 0.1])
    sig_rx = sigma_a_reaction("U238", "z_2n", group_struct=E_g)
    observed = (0.0 <= sig_rx).all()
    assert observed
    sig_rx = sigma_a_reaction("U238", "gamma", group_struct=E_g)
    observed = (0.0 <= sig_rx).all()
    assert observed
    sig_rx = sigma_a_reaction("H1", "gamma")
    observed = (0.0 <= sig_rx).all()
    assert observed