def _improve_latex(s):
    """Improve an OSIRIS-generated latex string using common rules."""
    # Descriptive subindexes in roman
    s2 = s.replace(r"\omega_p", r"\omega_{\mathrm{p}}")
    s2 = s2.replace("m_e", r"m_{\mathrm{e}}")
    # "Arbitrary units" in roman
    s2 = s2.replace("a.u.", r"\mathrm{a.u.}")
    return s2