def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def transientsc(bch, title=''):
    """creates a transient short circuit plot"""
    cols = 1
    rows = 2
    htitle = 1.5 if title else 0
    fig, ax = plt.subplots(nrows=rows, ncols=cols,
                           figsize=(10, 3*rows + htitle))
    if title:
        fig.suptitle(title, fontsize=16)

    row = 1
    plt.subplot(rows, cols, row)
    ax = plt.gca()
    ax.set_title('Currents / A')
    ax.grid(True)
    for i in ('ia', 'ib', 'ic'):
        ax.plot(bch.scData['time'], bch.scData[i], label=i)
    ax.set_xlabel('Time / s')
    ax.legend()

    row = 2
    plt.subplot(rows, cols, row)
    ax = plt.gca()
    ax.set_title('Torque / Nm')
    ax.grid(True)
    ax.plot(bch.scData['time'], bch.scData['torque'])
    ax.set_xlabel('Time / s')

    fig.tight_layout(h_pad=2)
    if title:
        fig.subplots_adjust(top=0.92)