Removes unused sum_true method.

zipline/gens/utils.py

@@ -106,14 +106,6 @@ def create_trade(sid, price, amount, datetime, source_id="test_factory"):
     return row
 
 
-def sum_true(bool_iterable):
-    """
-    Takes an iterable of boolean values and returns the number of
-    those values that are True.
-    """
-    return sum(map(int, bool_iterable))
-
-
 def assert_datasource_protocol(event):
     """Assert that an event meets the protocol for datasource outputs."""