def __next__(self):
        if self._leftover:
            output = self._leftover
            self._leftover = b''
        else:
            output = next(self._producer)
            self._unget_history = []
        self.position += len(output)
        return output
Used when the exact number of bytes to read is unimportant.
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/Django-1.6.10/django/http/multipartparser.py/LazyStream.__next__