{"msg":{"caption":"trace output","file_name":"f","pos_col":2,"pos_line":3,"severity":"information","text":"foo\n"},"response":"additional_message"}
{"msg":{"caption":"trace output","file_name":"f","pos_col":2,"pos_line":5,"severity":"information","text":"hello world\n"},"response":"additional_message"}
{"message":"file invalidated","response":"ok","seq_num":0}