FATAL                   Log levels
appender_console        Append log record to stdout
appender_file           Append log messages to a file
appender_pushbullet     Send log messages to Pushbullet
appender_slack          Send log messages to a Slack channel
appender_tee            Append log messages to a file and stdout as
                        well
colorize_by_log_level   Colorize string by the related log level
formatter_glue          Apply 'glue' to convert R objects into a
                        character vector
formatter_glue_or_sprintf
                        Apply 'glue' and 'sprintf'
formatter_logging       Mimic the default formatter used in the
                        'logging' package
formatter_paste         Concatenate R objects into a character vector
                        via 'paste'
formatter_sprintf       Apply 'sprintf' to convert R objects into a
                        character vector
get_logger_meta_variables
                        Collect useful information about the logging
                        environment to be used in log messages
grayscale_by_log_level
                        Render a string with light/dark gray based on
                        the related log level
layout_glue             Format a log message with 'glue'
layout_glue_colors      Format a log message with 'glue' and ANSI
                        escape codes to add colors
layout_glue_generator   Generate log layout function using common
                        variables available via glue syntax
layout_json             Generate log layout function rendering JSON
layout_logging          Format a log record as the logging package does
                        by default
layout_simple           Format a log record by concatenating the log
                        level, timestamp and message
log_appender            Get or set log record appender function
log_eval                Evaluate an expression and log results
log_formatter           Get or set log message formatter
log_layout              Get or set log record layout
log_level               Log a message with given log level
log_threshold           Get or set log level threshold
logger                  Generate logging utility
skip_formatter          Adds the skip_formatter attribute to an object
                        so that logger will skip calling the formatter
                        function on the object(s) to be logged
with_log_threshold      Evaluate R expression with a temporarily
                        updated log level threshold
