def _cmp_key(self, obj=None):
if not obj:<EOL><INDENT>obj = self<EOL><DEDENT>line_nr = int(obj.line_nr) if obj.line_nr else <NUM_LIT:0><EOL>col = int(obj.col) if obj.col else <NUM_LIT:0><EOL>return (obj.path, line_nr, col, obj.msg)<EOL>
Comparison key for sorting results from all linters.

        The sort should group files and lines from different linters to make it
        easier for refactoring.