gf, ps, svg, template

        or a string of the form: ``module://my.module.name``.

        Switching to an interactive backend is not possible if an unrelated
        event loop has already been started (e.g., switching to GTK3Agg if a
        TkAgg window has already been opened).  Switching to a non-interactive
        backend is always possible.

    force : bool, default: True
        If True (the default), raise an `ImportError` if the backend cannot be
        set up (either because it fails to import, or because an incompatible
        GUI interactive framework is already running); if False, silently
        ignore the failure.

    See Also
    --------
    :ref:`backends`
    matplotlib.get_backend
    matplotlib.pyplot.switch_backend

    z