def mode(collection):
    # build dictionary from element -> number of occurrences
    count = {}
    for v in collection:
        count[v] = 1 + count.get(v, 0)

    # loop through results and keep track of item with greatest number
    mode = None
    bigCount = 0
    for item,num in count.items():
        if num >= bigCount:
            mode = item
            bigCount = num

    return mode