Returns the gesture(s) in `gestureList` that closest matches the gesture in
    `strokes`. The `maxDifference` is how many differences there can be and still
    be considered a match.

def findClosestMatchingGesture(strokes, gestureList, maxDifference=None):
    """
    Returns the gesture(s) in `gestureList` that closest matches the gesture in
    `strokes`. The `maxDifference` is how many differences there can be and still
    be considered a match.
    """
    if len(gestureList) == 0:
        return None

    #gestureList = [list(frozenset(tuple(gesture))) for gesture in gestureList] # make a unique list
    gestureList = frozenset([tuple(gesture) for gesture in gestureList])
    distances = {}
    for g in gestureList:
        levDist = levenshteinDistance(strokes, g)
        if maxDifference is None or levDist <= maxDifference:
            distances.setdefault(levDist, [])
            distances[levDist].append(g)

    if not distances:
        return None # No matching gestures are within the tolerance of maxDifference.

    return tuple(distances[min(distances.keys())])