def _index_for(self, minified_src):
        if minified_src not in self._indices:
            with open(os.path.join(self._dir, minified_src + '.map')) as fp:
                self._indices[minified_src] = sourcemap.load(fp)

        return self._indices[minified_src]
Return the source map index for minified_src, loading it if not
dataset/ETHPy150Open zulip/zulip/zerver/lib/unminify.py/SourceMap._index_for