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diff --git a/src/python/_framework/foundation/stream_util.py b/src/python/_framework/foundation/stream_util.py
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+++ b/src/python/_framework/foundation/stream_util.py
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+# Copyright 2015, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Helpful utilities related to the stream module."""
+
+import logging
+import threading
+
+from _framework.foundation import stream
+
+_NO_VALUE = object()
+
+
+class TransformingConsumer(stream.Consumer):
+  """A stream.Consumer that passes a transformation of its input to another."""
+
+  def __init__(self, transformation, downstream):
+    self._transformation = transformation
+    self._downstream = downstream
+
+  def consume(self, value):
+    self._downstream.consume(self._transformation(value))
+
+  def terminate(self):
+    self._downstream.terminate()
+
+  def consume_and_terminate(self, value):
+    self._downstream.consume_and_terminate(self._transformation(value))
+
+
+class IterableConsumer(stream.Consumer):
+  """A Consumer that when iterated over emits the values it has consumed."""
+
+  def __init__(self):
+    self._condition = threading.Condition()
+    self._values = []
+    self._active = True
+
+  def consume(self, stock_reply):
+    with self._condition:
+      if self._active:
+        self._values.append(stock_reply)
+        self._condition.notify()
+
+  def terminate(self):
+    with self._condition:
+      self._active = False
+      self._condition.notify()
+
+  def consume_and_terminate(self, stock_reply):
+    with self._condition:
+      if self._active:
+        self._values.append(stock_reply)
+        self._active = False
+        self._condition.notify()
+
+  def __iter__(self):
+    return self
+
+  def next(self):
+    with self._condition:
+      while self._active and not self._values:
+        self._condition.wait()
+      if self._values:
+        return self._values.pop(0)
+      else:
+        raise StopIteration()
+
+
+class ThreadSwitchingConsumer(stream.Consumer):
+  """A Consumer decorator that affords serialization and asynchrony."""
+
+  def __init__(self, sink, pool):
+    self._lock = threading.Lock()
+    self._sink = sink
+    self._pool = pool
+    # True if self._spin has been submitted to the pool to be called once and
+    # that call has not yet returned, False otherwise.
+    self._spinning = False
+    self._values = []
+    self._active = True
+
+  def _spin(self, sink, value, terminate):
+    while True:
+      try:
+        if value is _NO_VALUE:
+          sink.terminate()
+        elif terminate:
+          sink.consume_and_terminate(value)
+        else:
+          sink.consume(value)
+      except Exception as e:  # pylint:disable=broad-except
+        logging.exception(e)
+
+      with self._lock:
+        if terminate:
+          self._spinning = False
+          return
+        elif self._values:
+          value = self._values.pop(0)
+          terminate = not self._values and not self._active
+        elif not self._active:
+          value = _NO_VALUE
+          terminate = True
+        else:
+          self._spinning = False
+          return
+
+  def consume(self, value):
+    with self._lock:
+      if self._active:
+        if self._spinning:
+          self._values.append(value)
+        else:
+          self._pool.submit(self._spin, self._sink, value, False)
+          self._spinning = True
+
+  def terminate(self):
+    with self._lock:
+      if self._active:
+        self._active = False
+        if not self._spinning:
+          self._pool.submit(self._spin, self._sink, _NO_VALUE, True)
+          self._spinning = True
+
+  def consume_and_terminate(self, value):
+    with self._lock:
+      if self._active:
+        self._active = False
+        if self._spinning:
+          self._values.append(value)
+        else:
+          self._pool.submit(self._spin, self._sink, value, True)
+          self._spinning = True