def row_gen_for_source(self, source_name, use_row_spec = True):

        source = self.metadata.sources[source_name]

        fn = self.filesystem.download(source_name)

        if fn.endswith('.zip'):
            sub_file = source.file
            fn = self.filesystem.unzip(fn, regex=sub_file)
            
        return DelimitedRowGenerator(fn, delimiter = '\t')