def purge_duplicates(list_in):
    """Remove duplicates from list while preserving order.

    Parameters
    ----------
    list_in: Iterable

    Returns
    -------
    list
        List of first occurences in order
    """
    _list = []
    for item in list_in:
        if item not in _list:
            _list.append(item)
    return _list