count occurences in a list of lists
    >>> count([['a','b'],['a']])
    defaultdict(int, {'a' : 2, 'b' : 1})

def count(args):
    """ count occurences in a list of lists
    >>> count([['a','b'],['a']])
    defaultdict(int, {'a' : 2, 'b' : 1})
    """
    counts = defaultdict(int)
    for arg in args:
        for item in arg:
            counts[item] = counts[item] + 1
    return counts