def min_list(lst):
    """
    A helper function for finding the minimum of a list of integers where some of the entries might be None.
    """
    if len(lst) == 0:
        return None
    elif len(lst) == 1:
        return lst[0]
    elif all([entry is None for entry in lst]):
        return None
    return min([entry for entry in lst if entry is not None])