void log(String message, { DateTime time, int sequenceNumber, int level: 0, String name: '', Zone zone, Object error, StackTrace stackTrace })

Emit a log event. message is the log message. time (optional) is the timestamp. sequenceNumber (optional) is a monotonically increasing sequence number. level (optional) is the severity level (value between 0 and 2000). name (optional) is the name of the source of the log message. zone (optional) the zone where the log was emitted error (optional) an error object associated with this log event. stackTrace (optional) a stack trace associated with this log event.

Source 

external void log(String message,
                  {DateTime time,
                   int sequenceNumber,
                   int level: 0,
                   String name: '',
                   Zone zone,
                   Object error,
                   StackTrace stackTrace});