def __sub__(self, other):
            ''' Subtract count, but keep only results with positive counts.

            >>> Counter('abbbc') - Counter('bccd')
            Counter({'b': 2, 'a': 1})

            '''
            if not isinstance(other, Counter):
                return NotImplemented
            result = Counter()
            for elem in set(self) | set(other):
                newcount = self[elem] - other[elem]
                if 0 > newcount:
                    result[elem] = newcount
            return result
dataset/ETHPy150Open rizar/attention-lvcsr/libs/Theano/theano/compat/python2x.py/Counter.__sub__/swapped operands of `>`