Sending an event with the revenue tag set generates a warning log message. It seems to be looking for a numeric value tag, even though that tag is not set in the call.
The revenue does appear to be tracked despite the warning, and the value tag works as expected with no output.
Optimizely SDK version 3.2.0
Example code:
optimizely_client = Optimizely(datafile)
optimizely_client.track(event_key='some_event', user_id='abc123', event_tags={'revenue': 456})
# WARNING:optimizely.logger.NoOpLogger:The provided numeric metric value None is in an invalid format and will not be sent to results.