diff --git a/src/filter.py b/src/filter.py
index 9df5d75..8c0a37e 100644
--- a/src/filter.py
+++ b/src/filter.py
@@ -281,14 +281,6 @@ class Filter(object):
         extractor = NumpyClient(self.src.url).stream_extract_numpy
         inserter = NumpyClient(self.dest.url).stream_insert_numpy_context
 
-        # Format output data.
-        formatter = lambda row: " ".join([repr(x) for x in row]) + "\n"
-
-        def batch(iterable, size):
-            c = itertools.count()
-            for k, g in itertools.groupby(iterable, lambda x: c.next() // size):
-                yield g
-
         for interval in self.intervals():
             print "Processing", self.interval_string(interval)
             with inserter(self.dest.path,