return_lines = function () {
            if (read_id !== last_read_id && !self.input_stream.end) {
                //Wait for a previous request to return lines
                utils.tick(return_lines);
            } else {
                last_read_id++;
                callback(self.input_stream.lines.length ? self.input_stream.lines.splice(0, num) : false);
            }
        }
Returns lines (\n or \r\n terminated) from the input stream. Lines are returned
in the same order as they are requested.

@param {Number} start
@param {Number} num
@param {Function} callback
@api public