def METHOD_NAME(name):
    """Is a certain set of data available?"""
    if name == "gammapy-extra":
        return "GAMMAPY_EXTRA" in os.environ
    elif name == "gammapy-data":
        return "GAMMAPY_DATA" in os.environ
    elif name == "gamma-cat":
        return "GAMMA_CAT" in os.environ
    elif name == "fermi-lat":
        return "GAMMAPY_FERMI_LAT_DATA" in os.environ
    else:
        raise ValueError(f"Invalid name: {name}")