def get_file_to_edit(self):
        # type: () -> Optional[str]
        """Returns the file with highest priority in configuration
        """
        assert self.load_only is not None, \
            "Need to be specified a file to be editing"

        try:
            return self._get_parser_to_modify()[0]
        except IndexError:
            return None
Returns the file with highest priority in configuration
        
product/gradle-plugin/src/main/python/pip/_internal/configuration.py