Add a note about row_log_interval=50 default to logging doc page or warning
from #3760
"Okay, noticing that the loss was getting logged every 50 mini-batches eventually led me to the answer. The Trainer class constructor has a parameter, row_log_interval, that controls how often the on_step logging metrics are actually logged, and the default value is 50. I ran the above experiment with row_log_interval set to 1 and ended up with 3,500 loss values logged, just as expected.
This seems like an important bit of information that is currently missing from the logging documentation. At the very least, I'd wager that other users are likely to be confused by this, too, and also conclude that logging isn't working as expected. So, this is not a software bug as I originally thought, but a problem of missing information in the documentation."