Fixed #286. Convert existing _format_report to the new format_report method.

The rationael behind is that the old one would require new signatures to be added.
The new one might be a bit ugly in terms of all the braces and brackets, but
usage wise it's pretty consistent and simple.
Merge pull request #290 from yeukhon/issue#286

Fixed #286. Convert existing _format_report to the new format_report method