def readline(self, size=-1):
        if size == 0:
            return b('')

        remainder = int(self.length) - self.__position
        if size < 0 or size > remainder:
            size = remainder

        received = 0
        data = StringIO()
        while received < size:
            chunk_data = self.readchunk()
            pos = chunk_data.find(NEWLN, 0, size)
            if pos != -1:
                size = received + pos + 1

            received += len(chunk_data)
            data.write(chunk_data)
            if pos != -1:
                break

        self.__position -= received - size

        # Return 'size' bytes and store the rest.
        data.seek(size)
        self.__buffer = data.read()
        data.seek(0)
        return data.read(size)
Read one line or up to `size` bytes from the file.
dataset/ETHPy150Open blynch/CloudMemeBackend/gridfs/grid_file.py/GridOut.readline