fix preview

wikipedia.py

@@ -470,8 +470,8 @@ class Wikipedia(datasets.ArrowBasedBuilder):
         """This function returns the examples in the raw (text) form."""
         logger.info("generating examples from = %s", filepath)
 
-        pf = pq.ParquetFile(filepath)
-
-        for group_i in range(pf.num_row_groups):
-            tbl = pf.read_row_group(group_i)
-            yield group_i, tbl
+        with open(filepath, "rb") as f:
+            pf = pq.ParquetFile(filepath)
+            for group_i in range(pf.num_row_groups):
+                tbl = pf.read_row_group(group_i)
+                yield group_i, tbl