def add_one(input):
    """
    Returns the list with 1 added to every element of input

    Example: add_one([1,2,3,1]) returns [2,3,4,2]

    Parameter input: The data to process
    Precondition: input an iterable, each element an int
    """
    result = []
    for x in input:
        x = x+1
        result.append(x)
    return result