(minuend, subtrahend)
return itertools.filterfalse(set(subtrahend).__contains__, minuend)
Return items in minuend not in subtrahend, retaining order
    with O(1) lookup.
Return items in minuend not in subtrahend, retaining order
    with O(1) lookup.
Return items in minuend not in subtrahend retaining order with O ( 1 ) lookup .
def _difference(minuend, subtrahend):
    """
    Return items in minuend not in subtrahend, retaining order
    with O(1) lookup.
    """
    return itertools.filterfalse(set(subtrahend).__contains__, minuend)
def _difference ( minuend , subtrahend ) : return itertools . filterfalse ( set ( subtrahend ) . __contains__ , minuend )