String format method (python2.6) was is entirely supported.

Consider this:

```python
def format_something(arg1):
    astring = "{0}-{1}-{2} ...its {this}!"
    return astring.format('3', '2', '1', this=arg1)
print format_something('the end')
```
It will fail, it needs to be added to the _STRING_FUNCTIONS with kwargs