'Remove any duplicate and empty paths from this multi-path'

def clean(self):

    mp = S3MultiPath(self)
    pop = mp.paths.pop
    self.paths = []
    append = self.paths.append
    while len(mp):
        item = pop(0)
        if (len(item) and (not (mp & item)) and (not (self & item))):
            append(item)
    return self
