def sum_list(lst):
    """Sum all elements in list

    :param l: List containing elements to sum
    :return: The sum of all elements in the list
    :rtype: int
    :raises ValueError: If there is any non-integer element on the list
    """
    if not all([isinstance(elem, int) for elem in lst]):
        raise ValueError("All elements on the list must be integers!")
    return sum(lst)