AppenderDbi             Log to databases via DBI
AppenderDigest          Abstract class for digests (multi-log message
                        notifications)
AppenderDt              Log to an in-memory data.table
AppenderGmail           Send emails via the Gmail REST API
AppenderMail            Abstract class for email Appenders
AppenderPushbullet      Send push-notifications via RPushbullet
AppenderSendmail        Send emails via sendmailR
AppenderSyslog          Log to the POSIX system log
LayoutDbi               Format log events for output to databases
Serializer              Serializers
select_dbi_layout       Automatically select appropriate layout for
                        logging to a database
unpack_json_cols        Unserialize data frame columns that contain
                        JSON
