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 psidq(bch):
    """creates the surface plots of a BCH reader object
    with a psid-psiq identification"""
    id = bch.psidq['id']
    iq = bch.psidq['iq']
    torque = bch.psidq['torque']
    ld = np.array(bch.psidq_ldq['ld'])
    lq = np.array(bch.psidq_ldq['lq'])
    psim = bch.psidq_ldq['psim']
    psid = bch.psidq['psid']
    psiq = bch.psidq['psiq']

    rows = 3
    fig = plt.figure(figsize=(10, 4*rows))
    fig.suptitle('Psid-Psiq Identification {}'.format(
        bch.filename), fontsize=16)

    fig.add_subplot(rows, 2, 1, projection='3d')
    idq_torque(id, iq, torque)

    fig.add_subplot(rows, 2, 2, projection='3d')
    idq_psid(id, iq, psid)

    fig.add_subplot(rows, 2, 3, projection='3d')
    idq_psiq(id, iq, psiq)

    fig.add_subplot(rows, 2, 4, projection='3d')
    idq_psim(id, iq, psim)

    fig.add_subplot(rows, 2, 5, projection='3d')
    idq_ld(id, iq, ld)

    fig.add_subplot(rows, 2, 6, projection='3d')
    idq_lq(id, iq, lq)