def _mixup( self, ps ):
for i in range(len(ps) - <NUM_LIT:1>, <NUM_LIT:0>, -<NUM_LIT:1>):<EOL><INDENT>j = int(numpy.random.random() * i)<EOL>temp = ps[i]<EOL>ps[i] = ps[j]<EOL>ps[j] = temp<EOL><DEDENT>return ps<EOL>
Private method to mix up a list of values in-place using a Fisher-Yates
        shuffle (see https://en.wikipedia.org/wiki/Fisher-Yates_shuffle).

        :param ps: the array
        :returns: the array, shuffled in-place