def _read_group_h5(filename, groupname):
    """Return group content.

    Args:
        filename (:class:`pathlib.Path`): path of hdf5 file.
        groupname (str): name of group to read.
    Returns:
        :class:`numpy.array`: content of group.
    """
    with h5py.File(filename, 'r') as h5f:
        data = h5f[groupname][()]
    return data