def __call__(eventDict):
        """
        Log an event.

        @type eventDict: C{dict} with C{str} keys.
        @param eventDict: A dictionary with arbitrary keys.  However, these
            keys are often available:
              - C{message}: A C{tuple} of C{str} containing messages to be
                logged.
              - C{system}: A C{str} which indicates the "system" which is
                generating this event.
              - C{isError}: A C{bool} indicating whether this event represents
                an error.
              - C{failure}: A L{failure.Failure} instance
              - C{why}: Used as header of the traceback in case of errors.
              - C{format}: A string format used in place of C{message} to
                customize the event.  The intent is for the observer to format
                a message by doing something like C{format % eventDict}.
        """

        Log an event.

        @type eventDict: C{dict} with C{str} keys.
        @param eventDict: A dictionary with arbitrary keys.  However, these
            keys are often available:
              - C{message}: A C{tuple} of C{str} containing messages to be
                logged.
              - C{system}: A C{str} which indicates the "system" which is
                generating this event.
              - C{isError}: A C{bool} indicating whether this event represents
                an error.
              - C{failure}: A L{failure.Failure} instance
              - C{why}: Used as header of the traceback in case of errors.
              - C{format}: A string format used in place of C{message} to
                customize the event.  The intent is for the observer to format
                a message by doing something like C{format % eventDict}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/log.py