How to use the covimerage.logger.logger.error function in covimerage

def map_functions(self, functions):
        while functions:
            prev_count = len(functions)
            for f in functions:
                if self.map_function(f):
                    functions.remove(f)
            new_count = len(functions)
            if prev_count == new_count:
                break

        for f in functions:
            logger.error('Could not find source for function: %s', f.name)