def get_ext(self, format=None, **kwargs):
try:<EOL><INDENT>format = format or self.default_params['<STR_LIT>']<EOL>return "<STR_LIT>" % format.lower()<EOL><DEDENT>except KeyError: pass<EOL>
Returns new file extension based on a processor's `format` parameter.
        Overwrite if different extension should be set ex: `'.txt'` or `None` if this 
        processor does not change file's extension.