def partial_flatten(l):
    """Flattens first layer of lists
    i.e.: [1,[2],[[3]]] -> [1,2,[3]]

    Parameters
    ----------
    l : list
        the list we wish to partially flatten

    Returns
    -------
    _list : list
        the list that has been partially flattened

    """
    _list = []
    for sublist in l:
        if isinstance(sublist, list):
            for item in sublist:
                _list.append(item)
        else:
            _list.append(sublist)
    return _list