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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def main(self, config_filename, file_names=None):
 """ Loads stored routines into the current schema. :param str config_filename: The name of the configuration file of the current project :param list[str] file_names: The sources that must be loaded. If empty all sources (if required) will loaded. :rtype: int The status of exit. """

        self._io.title('Loader')

        if file_names:
            self.__load_list(config_filename, file_names)
        else:
            self.__load_all(config_filename)

        if self.error_file_names:
            self.__log_overview_errors()
            return 1
        else:
            return 0