code: func NewJSONLogger(cfg *LogConfig, writer io.Writer) *JSONLogger {
  	l := &JSONLogger{json.NewEncoder(writer), cfg}
  	if l.cfg == nil {
  		l.cfg = &LogConfig{}
  	}
  	return l
  }
docs: // NewJSONLogger creates a new EVM tracer that prints execution steps as JSON objects
  // into the provided stream.