streamthinca.py: create a new background collector for background estimation.

gstlal-inspiral/python/streamthinca.py

@@ -221,6 +221,19 @@ class backgroundcollector(object):
 		return [event for event in map(index.__getitem__, background_ids) if event.snr >= snr_min]
 
 
+class timereversebackgroundcollector(object):
+	def __init__(self):
+		self.events = set()
+
+	def push(self, event_ids, offset_vector):
+		# input parameters are just for compatibility
+		self.events.update(event_ids)
+
+	def pull(self, snr_min, two_or_more_instruments, flushed_events):
+		# input parameters are just for compatibility
+		return [event for event in flushed_events if event.snr >= snr_min]
+
+
 class StreamThinca(object):
 	def __init__(self, xmldoc, process_id, delta_t, min_instruments = 2, sngls_snr_threshold = None):
 		self.ln_lr_from_triggers = None